Gene Summary

Gene:CD99; CD99 molecule (Xg blood group)
Aliases: MIC2, HBA71, MIC2X, MIC2Y, MSK5X
Location:Xp22.33 and Yp11.2
Summary:The protein encoded by this gene is a cell surface glycoprotein involved in leukocyte migration, T-cell adhesion, ganglioside GM1 and transmembrane protein transport, and T-cell death by a caspase-independent pathway. In addition, the encoded protein may have the ability to rearrange the actin cytoskeleton and may also act as an oncosuppressor in osteosarcoma. This gene is found in the pseudoautosomal region of chromosomes X and Y and escapes X-chromosome inactivation. There is a related pseudogene located immediately adjacent to this locus. [provided by RefSeq, Mar 2016]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:CD99 antigen
Source:NCBIAccessed: 29 August, 2019


What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 29 August 2019 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 29 August, 2019 using data from PubMed, MeSH and CancerIndex

Specific Cancers (7)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Entity Topic PubMed Papers
-CD99 and Neuroectodermal Tumors, Primitive View Publications74
Bone Cancer (primary)CD99 and Bone Cancer View Publications62
Soft Tissue SarcomaCD99 and Soft Tissue Cancers View Publications43
Kidney CancerCD99 and Kidney Cancer View Publications31
Vulvar CancerCD99 and Vulvar Cancer View Publications9
Wilms TumourCD99 and Wilms Tumour View Publications7
Ewing's SarcomaMIC2 expression in the Differential Diagnosis of Ewing's Sarcoma
Unlike most other small blue cell tumors of childhood, Ewing's sarcoma and pPNET strongly express the MIC2(CD99) antigen. Therefore MIC2 analysis can be a useful part of the panel of tests used in the differential diagnosis of Ewing's sarcoma / pPNET.
See: More details below...

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

MIC2 expression in the Differential Diagnosis of Ewing's Sarcoma

Unlike most other small blue cell tumors of childhood, Ewing's sarcoma and pPNET strongly express the MIC2(CD99) antigen. Therefore MIC2 analysis can be a useful part of the panel of tests used in the differential diagnosis of Ewing's sarcoma / pPNET.

See also: Ewing's Sarcoma - Clinical and Research information

Latest Publications

Louati S, Senhaji N, Chbani L, Bennis S
Dis Markers. 2018; 2018:7971019 [PubMed] Free Access to Full Article Related Publications
Ewing sarcoma/primitive neuroectodermal tumor (Ewing/PNET sarcomas or EPS) are a group of round cell tumors. Malignant round cell tumors form a large and diverse group that includes rhabdomyosarcoma, synovial sarcoma, non-Hodgkin's lymphoma, neuroblastoma, hepatoblastoma, Wilm's tumor, desmoplastic small round cell tumor, and other morphologically similar entities. Differential diagnosis of Ewing sarcoma/primitive neuroectodermal tumor (Ewing/PNET sarcomas or EPS) is difficult. In addition to morphology and immunohistochemistry (IHC), differential diagnosis of these tumors is based on molecular analysis of the

Martinelli M, Parra A, Scapoli L, et al.
CD99 polymorphisms significantly influence the probability to develop Ewing sarcoma in earlier age and patient disease progression.
Oncotarget. 2016; 7(47):77958-77967 [PubMed] Free Access to Full Article Related Publications
Ewing sarcoma (EWS), the second most common primary bone tumor in pediatric age, is known for its paucity of recurrent somatic abnormalities. Apart from the chimeric oncoprotein that derives from the fusion of EWS and FLI genes, recent genome-wide association studies have identified susceptibility variants near the EGR2 gene that regulate DNA binding of EWS-FLI. However, to induce transformation, EWS-FLI requires the presence of additional molecular events, including the expression of CD99, a cell surface molecule with critical relevance for the pathogenesis of EWS. High expression of CD99 is a common and distinctive feature of EWS cells, and it has largely been used for the differential diagnosis of the disease. The present study first links CD99 germline genetic variants to the susceptibility of EWS development and its progression. In particular, a panel of 25 single nucleotide polymorphisms has been genotyped in a case-control study. The CD99 rs311059 T variant was found to be significantly associated [P value = 0.0029; ORhet = 3.9 (95% CI 1.5-9.8) and ORhom = 5.3 (95% CI 1.2-23.7)] with EWS onset in patients less than 14 years old, while the CD99 rs312257-T was observed to be associated [P value = 0.0265; ORhet = 3.5 (95% CI 1.3-9.9)] with a reduced risk of relapse. Besides confirming the importance of CD99, our findings indicate that polymorphic variations in this gene may affect either development or progression of EWS, leading to further understanding of this cancer and development of better diagnostics/prognostics for children and adolescents with this devastating disease.

Ishiguro M, Yuki M, Fukushige T, et al.
Molecular cytogenetic characterization of two established ESFT cell lines.
Hum Cell. 2017; 30(1):41-48 [PubMed] Related Publications
Ewing's sarcoma/primitive neuroectodermal tumor/Askin's tumor (Ewing`s sarcoma family of tumors: ESFT) is the most common type of malignant tumor of bone and soft tissue in children and young adults, and morphologically is a member of a group of small round cell tumors. We report, here, on the establishment of two human ESFT cell lines, FU-PNET-3 and FU-PNET-4, from the iliac and the chest wall, respectively, the cells of both cell lines were tumorigenic in immunodeficient mice. Histologically, both original and xenograft tumors and cultured cells were composed of small round cells with positive immunoreactivity for CD99 and Nkx2.2. Molecular biological examination demonstrated chimeric transcripts of EWSR1 exon 7 to FLI1 exon 6 in FU-PNET-3 cells, and EWSR1 exon 10 to FLI1 exon 6 in FU-PNET-4 cells. Cytogenetic analysis revealed chromosome translocation t(11;22)(q24;q12) and some secondary changes in both cultured cells. These histological, molecular biological, and cytogenetical findings indicate ESFT in both cell lines. ESFT is well studied, but its recurrent fusion genes are heterogeneous and its biological behaviors are unclear. The FU-PNET-3 and FU-PNET-4 cell lines have been well examined and may become useful tools for studying the genetic and biological behavioral properties of ESFT.

Kim SK, Park YK
Ewing sarcoma: a chronicle of molecular pathogenesis.
Hum Pathol. 2016; 55:91-100 [PubMed] Related Publications
Sarcomas have traditionally been classified according to their chromosomal alterations regardless of whether they accompany simple or complex genetic changes. Ewing sarcoma, a classic small round cell bone tumor, is a well-known mesenchymal malignancy that results from simple sarcoma-specific genetic alterations. The genetic alterations are translocations between genes of the TET/FET family (TLS/FUS, EWSR1, and TAF15) and genes of the E26 transformation-specific (ETS) family. In this review, we intend to summarize a chronicle of molecular findings of Ewing sarcoma including recent advances and explain resultant molecular pathogenesis.

Machado I, Navarro L, Pellin A, et al.
Defining Ewing and Ewing-like small round cell tumors (SRCT): The need for molecular techniques in their categorization and differential diagnosis. A study of 200 cases.
Ann Diagn Pathol. 2016; 22:25-32 [PubMed] Related Publications
BACKGROUND: Differentiation of Ewing sarcoma family of tumors (ESFT) and Ewing-like tumors remains problematic. Certain ESFT with morphological and immunohistochemical (IHC) profiles lack the EWSR1-ETS transcript. To improve diagnostic accuracy we investigated the presence of several specific transcripts in 200 small round cell tumors (SRCT) displaying ESFT morphology and immunophenotype in which EWSR1 FISH analysis was non-informative or negative.
DESIGN: 200 tumors (formalin-fixed, paraffin-embedded) were analyzed by RT-PCR. All tumors were tested for EWSR1-ETS, EWSR1/WT1, PAX3/7-FOX01 or SYT/SSX transcripts, and the negative tumors were subsequently analyzed for CIC/DUX4, BCOR/CCNB3 and CIC/FOX04 transcripts.
RESULTS: 133 (66.5%) ESFT displayed one of the above EWSR1-ETS translocations. Three cases (1.5%) revealed the SYT-SSX transcript for Synovial sarcoma, and one (0.5%) a EWSR1-WT1 transcript for Desmoplastic Small Round Cell tumor. The CIC-DUX4 translocation was found in six Ewing-like tumors (3%) with CD99 positivity. The BCOR-CCNB3 gene fusion was observed in 5 tumors (2.5%) displaying round or spindle cells with strong CCNB3 IHC expression in 3 tumors. Moreover, RT-PCR failed to detect any gene fusion transcripts in 19 tumors (9.5%) and were considered "undifferentiated small round cell sarcoma" (SRCS). Molecular biology results were non-informative in 33 SRCTs (16.5%) due to RNA degradation through inadequate fixation and/or decalcification.
CONCLUSION: Our analysis of 200 SRCTs confirms the molecular heterogeneity of neoplasms with ESFT morphology and highlight that molecular studies with RT-PCR including new emerging gene fusion transcripts are mandatory for the diagnosis when EWSR1 FISH is negative or non-informative. The incidence of CIC-DUX4, BCOR-CCNB3 and CIC-FOX04 transcripts was relatively low. A small group of Ewing-like sarcomas or undifferentiated SRCS remains unclassified. Adopting appropriate tissue fixation and processing protocols is important to avoid degradation of fixed/embedded tissue when no frozen tumor is available.

Chen S, Deniz K, Sung YS, et al.
Ewing sarcoma with ERG gene rearrangements: A molecular study focusing on the prevalence of FUS-ERG and common pitfalls in detecting EWSR1-ERG fusions by FISH.
Genes Chromosomes Cancer. 2016; 55(4):340-9 [PubMed] Free Access to Full Article Related Publications
The genetics of Ewing sarcoma (ES) are characterized by a canonical fusion involving EWSR1 gene and a member of the ETS family of transcription factors, such as FLI1 and ERG. In fact, ERG gene rearrangements represent the second most common molecular alteration, with EWSR1-ERG being identified in 5-10% of cases, while only a handful of reports document a FUS-ERG fusion. In this study, we focus on ES with ERG gene abnormalities, specifically to investigate the prevalence and clinicopathologic features of FUS-ERG fusions in a large cohort of small blue round cell tumors (SBRCTs) and compare to the eight reported FUS-positive ES. Among the 85 SBRCTs tested, seven (8.2%) cases harbored FUS gene rearrangements; six fused to ERG and one with FEV. During this investigation we came across a number of ERG-rearranged ES lacking both EWSR1 and FUS abnormalities by FISH. In one case, RNA sequencing identified an EWSR1-ERG transcript despite the negative EWSR1 rearrangements by FISH. Additional 3-color FISH fusion assay demonstrated the fusion of EWSR1 and ERG signals in all four cases negative for break-apart EWSR1 FISH. These results emphasize a potential pitfall of relying on EWSR1 FISH assay alone for diagnosis of ES. In cases with classic morphology and/or strong CD99 and ERG immunoreactivity, additional molecular testing should be applied, such as ERG FISH or RT-PCR/next generation sequencing, for a more definitive diagnosis. Although our study group is small, there were no differences noted between the clinical, morphologic features and immunoprofile of the different subsets of ERG-rearranged SBRCTs.

Yoshida A, Goto K, Kodaira M, et al.
CIC-rearranged Sarcomas: A Study of 20 Cases and Comparisons With Ewing Sarcomas.
Am J Surg Pathol. 2016; 40(3):313-23 [PubMed] Related Publications
The CIC gene rearrangement exists in a subset of small round cell sarcomas. As the nosologic relationship of these sarcomas to Ewing sarcomas remains undetermined, we examined 20 CIC-rearranged sarcomas to compare their clinicopathologic features with those of Ewing sarcomas. The CIC-rearranged sarcomas were from a group of 14 men and 6 women with a median age of 24.5 years. The primary tumor sites included the limbs, trunk wall, internal trunk, lung, cerebrum, and pharynx. A comparison of the demographic and clinical characteristics of the 20 patients with CIC-rearranged sarcomas with those of the 53 near-consecutive patients with EWSR1-rarranged Ewing sarcomas showed that there were no differences with respect to their ages and sexes. Although none of the CIC-rearranged sarcomas arose in the bone, 40% of the Ewing sarcomas primarily affected the skeleton. The overall survival of patients with Ewing sarcomas was significantly better than that for patients with CIC-rearranged sarcomas. A histologic comparison of the CIC-rearranged sarcomas with 20 EWSR1-rearranged Ewing sarcomas showed significantly higher degrees of lobulation, nuclear pleomorphism, the prominence of the nucleoli, spindle cell elements, and myxoid changes in the CIC-rearranged sarcomas. Distinguishing immunohistochemical features included heterogenous CD99 reactivity, nuclear WT1 expression, and calretinin expression in the CIC-rearranged sarcomas and NKX2.2 expression in the Ewing sarcomas. CIC-rearranged sarcomas are distinct from Ewing sarcomas clinically, morphologically, and immunohistochemically, and they should be considered a separate entity rather than being grouped within the same family of tumors.

Sugita S, Arai Y, Tonooka A, et al.
A novel CIC-FOXO4 gene fusion in undifferentiated small round cell sarcoma: a genetically distinct variant of Ewing-like sarcoma.
Am J Surg Pathol. 2014; 38(11):1571-6 [PubMed] Related Publications
Differential diagnosis of small round cell sarcomas (SRCSs) grouped under the Ewing sarcoma family of tumors (ESFT) can be a challenging situation for pathologists. Recent studies have revealed that some groups of Ewing-like sarcoma show typical ESFT morphology but lack any EWSR1-ETS gene fusions. Here we identified a novel gene fusion, CIC-FOXO4, in a case of Ewing-like sarcoma with a t(X;19)(q13;q13.3) translocation. The patient was a 63-year-old man who had an asymptomatic, 30-mm, well-demarcated, intramuscular mass in his right posterior neck, and imaging findings suggested a diagnosis of high-grade sarcoma. He was treated with complete resection and subsequent radiotherapy and chemotherapy. He was alive without local recurrence or distant metastasis 6 months after the operation. Histologic examination revealed SRCS with abundant desmoplastic fibrous stroma suggesting a desmoplastic small round cell tumor. Immunohistochemical analysis showed weak to moderate and partial staining for MIC2 (CD99) and WT1, respectively. High-throughput transcriptome sequencing revealed a gene fusion, and the genomic rearrangement between the CIC and FOXO4 genes was identified by fluorescence in situ hybridization. Aside from the desmoplastic stroma, the CIC-FOXO4 fusion sarcoma showed morphologic and immunohistochemical similarity to ESFT and Ewing-like sarcomas, including the recently described CIC-DUX4 fusion sarcoma. Although clinicopathologic analysis with additional cases is necessary, we conclude that CIC-FOXO4 fusion sarcoma is a new type of Ewing-like sarcoma that has a specific genetic signature. These findings have important implications for the differential diagnosis of SRCS.

Specht K, Sung YS, Zhang L, et al.
Distinct transcriptional signature and immunoprofile of CIC-DUX4 fusion-positive round cell tumors compared to EWSR1-rearranged Ewing sarcomas: further evidence toward distinct pathologic entities.
Genes Chromosomes Cancer. 2014; 53(7):622-33 [PubMed] Free Access to Full Article Related Publications
Round cell sarcomas harboring CIC-DUX4 fusions have recently been described as highly aggressive soft tissue tumors of children and young adults. Due to partial morphologic and immunohistochemical overlap with Ewing sarcoma (ES), CIC-DUX4-positive tumors have generally been classified as ES-like and managed similarly; however, a systematic comparison at the molecular and immunohistochemical levels between these two groups has not yet been conducted. Based on an initial observation that CIC-DUX4-positive tumors show nuclear immunoreactivity for WT1 and ETS transcription factors, FLI1 and ERG, we performed a detailed immunohistochemical and molecular analysis including these markers, to further investigate the relationship between CIC-DUX4 tumors and ES. The study group included 21 CIC-DUX4-positive sarcomas and 20 EWSR1-rearranged ES. Immunohistochemically, CIC-DUX4 sarcomas showed membranous CD99 positivity in 18 (86%) cases, but only 5 (24%) with a diffuse pattern, while WT1 and FLI1 were strongly positive in all cases. ERG was positive in 18% of cases. All ES expressed CD99 and FLI1, while ERG positivity was only seen in EWSR1-ERG fusion positive ES. WT1 was negative in all ES. Expression profiling validated by q-PCR revealed a distinct gene signature associated with CIC-DUX4 fusion, with upregulation of ETS transcription factors (ETV4, ETV1, and ETV5) and WT1, among top overexpressed genes compared to ES, other sarcomas and normal tissue. In conclusion, the distinct gene signature and immunoprofile of CIC-DUX4 sarcomas suggest a distinct pathogenesis from ES. The consistent WT1 expression may provide a useful clue in the diagnosis in the context of round cell sarcomas negative for EWSR1 rearrangement. © 2014 Wiley Periodicals, Inc.

Amaral AT, Manara MC, Berghuis D, et al.
Characterization of human mesenchymal stem cells from ewing sarcoma patients. Pathogenetic implications.
PLoS One. 2014; 9(2):e85814 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Ewing Sarcoma (EWS) is a mesenchymal-derived tumor that generally arises in bone and soft tissue. Intensive research regarding the pathogenesis of EWS has been insufficient to pinpoint the early events of Ewing sarcomagenesis. However, the Mesenchymal Stem Cell (MSC) is currently accepted as the most probable cell of origin.
MATERIALS AND METHODS: In an initial study regarding a deep characterization of MSC obtained specifically from EWS patients (MSC-P), we compared them with MSC derived from healthy donors (MSC-HD) and EWS cell lines. We evaluated the presence of the EWS-FLI1 gene fusion and EWSR1 gene rearrangements in MSC-P. The presence of the EWS transcript was confirmed by q-RT-PCR. In order to determine early events possibly involved in malignant transformation, we used a multiparameter quantitative strategy that included both MSC immunophenotypic negative/positive markers, and EWS intrinsic phenotypical features. Markers CD105, CD90, CD34 and CD45 were confirmed in EWS samples.
RESULTS: We determined that MSC-P lack the most prevalent gene fusion, EWSR1-FLI1 as well as EWSR1 gene rearrangements. Our study also revealed that MSC-P are more alike to MSC-HD than to EWS cells. Nonetheless, we also observed that EWS cells had a few overlapping features with MSC. As a relevant example, also MSC showed CD99 expression, hallmark of EWS diagnosis. However, we observed that, in contrast to EWS cells, MSC were not sensitive to the inhibition of CD99.
CONCLUSIONS: In conclusion, our results suggest that MSC from EWS patients behave like MSC-HD and are phenotypically different from EWS cells, thus raising important questions regarding MSC role in sarcomagenesis.

White JC, Halligan GE, de Chadarévian JP, et al.
Unusual genetic aberrations including a deletion of KLF6 tumor suppressor gene revealed by integrated cytogenetic approaches in a pediatric ewing sarcoma.
J Pediatr Hematol Oncol. 2015; 37(1):e51-4 [PubMed] Related Publications
Ewing sarcoma is the third most common sarcoma in children and young adults. Its characteristic chromosomal rearrangement results in a chimerical EWSR1-ETS transcription factor. Secondary genetic alterations are very common. Membranous expression of CD99 is seen in almost all tumors. We report 2 unusual cytogenetic findings in a pediatric Ewing sarcoma, an insertion of the MIC2 gene encoding CD99 from Xp to 10p and a submicroscopic deletion of the well-known tumor supressor gene KLF6. The latter has not been described previously in pediatric neoplasms. Molecular pathways in tumorigenesis and genetic complexity in cancer are discussed.

Rekhi B, Vogel U, Basak R, et al.
Clinicopathological and molecular spectrum of ewing sarcomas/PNETs, including validation of EWSR1 rearrangement by conventional and array FISH technique in certain cases.
Pathol Oncol Res. 2014; 20(3):503-16 [PubMed] Related Publications
Over the years, a wide clinicopathological spectrum has been identified within Ewing family of tumors (EFTs). As these tumors are chemosensitive, their correct and timely identification is necessary. The aims of this study were (1) to present the diverse clinicopathological and molecular profile of EFTs in our settings, (2) to identify a pragmatic approach for diagnosing EFTs, especially for application of ancillary techniques, namely RT-PCR for specific transcripts (EWS-FLI1, EWS-ERG) and FISH for EWSR1 gene rearrangement, in certain cases and (3) to show the utility of tissue microarray in establishing a new FISH test. Fifty-eight EFTs were identified in 38 males and 20 females within an age-range of 1-65 years (median, 16), mostly in lower extremities (14) (24.1 %). Therapeutically, most patients underwent neoadjuvant chemotherapy with subsequent surgery. Histopathologically, diagnosis of EFTs was initially offered in 41/58 (70.6 %) tumors. On review, 59 % tumors showed diffuse pattern, while 41 % displayed rosettes. Immunohistochemically, tumor cells were mostly diffusely positive for CD99 (48/52) (92.3 %); FLI-1 (17/18) (94.4 %); variably for BCL2 (16/18) (88.8 %), synaptophysin (6/20) (35 %), S100-P (2/7) (28.5 %), CD56 (2/5) (40 %), NSE (2/5) (40 %), calponin (3/4) (75 %), EMA (5/24) (20.8 %) and CK (3/24) (12.5 %), the latter two mostly focally. Fifty five tumors were EWS-FLI1 positive, while a single tumor was EWS-ERG positive. Sensitivity for PCR was 61 %. EWSR1 rearrangement was detected by FISH in 12/13 Ewing sarcomas/PNETs. Sensitivity for EWSR1 test was 92.3 % and specificity was 100 %. Thirty-eight tumors, including 14 molecular confirmed EFTs and 21 other tumors were tested for EWSR1 rearrangement. Among 21 unrelated tumors, EWSR1 rearrangement was detected in few myoepithelial tumors, occasional desmoplastic small round cell tumor and an extraskeletal myxoid chondrosarcoma. Further, a tissue microarray with a separate set of 8 EFTs, confirmed at another laboratory was analysed for validation of EWSR1 rearrangement test. 23/28 (82.1 %) tissue cores of the tissue microarray, stained by FISH were interpretable, including EWSR1 rearrangement, detected in 20/28 tissue cores; not detected in 3 liver cores and uninterpretable in 5 (17.8 %) cores. Classical EFTs can be diagnosed with diffuse, membranous CD99 positivity, intranuclear FLI1 positivity and LCA negativity in malignant round cells. In unconventional cases, it is indispensable to reveal the concomitant fusion m-RNA by RT-PCR. In case of negative molecular results, it is necessary to prove EWSR1 rearrangement by FISH. These tests should be interpreted with clinicopathological correlation. Tissue microarrays for FISH are useful during validation of a new test, especially when sarcomas like EFTs show less genetic heterogeneity within tumor cells.

Franzetti GA, Laud-Duval K, Bellanger D, et al.
MiR-30a-5p connects EWS-FLI1 and CD99, two major therapeutic targets in Ewing tumor.
Oncogene. 2013; 32(33):3915-21 [PubMed] Related Publications
Ewing sarcoma is a pediatric bone tumor characterized in 85% of cases by the fusion between EWS and FLI1 genes that results in the expression of the EWS-FLI1 aberrant transcription factor. Histologically, the Ewing tumor expresses high levels of the CD99 membrane glycoprotein. It has been recently described that CD99 expression contributes to the Ewing tumor oncogenesis by modulating growth and differentiation of tumor cells. Different studies have also shown that overexpression of EWS-FLI1 induces CD99 expression in non-Ewing cells. At the opposite, the knockdown of EWS-FLI1 expression by siRNA approaches has no significant effect on CD99 mRNA level in Ewing cells. Here, by in vivo and in vitro studies, we show that while EWS-FLI1 inhibition has only slight effects on the amount of CD99 transcript, it induces a dramatic decrease of the CD99 protein expression level, hence suggesting post-transcriptional regulations, possibly mediated by microRNAs. To further investigate this issue, we identified a set of 91 miRNAs that demonstrate EWS-FLI1 modulation, three of them being predicted to bind CD99 3' untranslated region (30'UTR). Among these, we show that miR-30a-5p has the ability to interact with the 30'UTR region of CD99 and to regulate its expression. Moreover, the re-expression of miRNA-30a-5p in Ewing cell line induces decreased cell proliferation and invasion. In this study, we therefore show that miR-30a-5p constitutes a major functional link between EWS-FLI1 and CD99, two critical biomarkers and therapeutic targets in Ewing sarcoma.

Vural C, Uluoğlu O, Akyürek N, et al.
The evaluation of CD99 immunoreactivity and EWS/FLI1 translocation by fluorescence in situ hybridization in central PNETs and Ewing's sarcoma family of tumors.
Pathol Oncol Res. 2011; 17(3):619-25 [PubMed] Related Publications
Ewing's sarcoma family of tumors (ESFTs) are indicated by malignant, small, round and blue cell tumors of the bone and soft tissue. Gene rearrangements between EWS gene on chromosome 22q12 and members of the ETS gene family are common in and specific to ESFTs. Another defining characteristic of ESFTs is their membranous expression of the CD99. In contrast, such translocations and immunoreactivity are not found in central primitive neuroectodermal tumors (cPNETs). The aim of this study was to investigate the detection of EWS/FLI1 translocations and CD99 immunoreactivity in order to evaluate their clinicopathological features and their roles in the differential diagnosis of these tumors. In this study, we investigated CD99 immunoreactivity using immunohistochemistry and Ewing's sarcoma / Friend leukaemia virus integration 1 (EWS/FLI1) translocation using the fluorescence in situ hybridization (FISH) method in 23 cases. CD99 expression was detected in 10/11 (90%) ESFT cases and 2/7 cPNET cases. In 18 cases EWS/FLI1 translocation was examined using the FISH method. The EWS/FLI1 translocations were detected in 7/8 (87.5%) ESFTs cases, whereas non of 8 cPNET cases were detected with this translocation. One case could not be classified as either central or peripheral, showed EWS/FLI1 translocation. There was a statistically significant difference in CD99 expression (p = 0.0013) and EWS/FLI1 translocation (p = 0,002) between cPNETs and ESFTs cases. In conclusion, CD99 expression and EWS/FLI1 translocation are specific and sensitive markers in the diagnosis of ESFTs. However, these were often not found in cases of cPNET. Therefore, in the diagnosis of ESFTs, clinical, radiological, histopathological and immunohistochemical parameters should always be evaluated together.

Angel JR, Alfred A, Sakhuja A, et al.
Ewing's sarcoma of the kidney.
Int J Clin Oncol. 2010; 15(3):314-8 [PubMed] Related Publications
Primitive neuroectodermal tumors (PNETs) are small, round-cell tumors of neural crest origin classically found in the central nervous system (CNS) but more recently characterized in the periphery. Peripherally located PNETs (pPNETs) are members of the Ewing's sarcoma family of tumors (EFTs). Renal localization of pPNETs is very rare, is found in young adults, and is characterized by an aggressive clinical course and poor prognosis. We present the case of a young man with renal pPNET characterized by psuedorosette formation, cluster of differentiation 99 (CD 99+), focally positive for neuron-specific enolase (NSE), with cytogenetic findings of the translocation t(11;22)(q24;q12) and the unique abnormality of trisomy 7. To our knowledge, we report the first case of trisomy 7 and PNET.

Manduch M, Dexter DF, Ellis PM, et al.
Extraskeletal Ewing's sarcoma/primitive neuroectodermal tumor of the posterior mediastinum with t(11;22)(q24;q12).
Tumori. 2008 Nov-Dec; 94(6):888-91 [PubMed] Related Publications
Ewing's sarcoma/primitive neuroectodermal tumor family of tumors is part of a rare group of malignant neoplasms with small round-cell morphology. We describe a 24-year-old woman who presented with non-specific back pain. A chest radiograph and magnetic resonance imaging demonstrated an extraosseous, dumbbell-shaped mass of the posterior mediastinum with extension into the spinal canal. The patient underwent a left posterolateral thoracotomy and a T3-5 laminectomy with subsequent multi-agent chemotherapy. Histopathologic examination of the tumor demonstrated sheets of primitive small round malignant cells that showed no visible differentiation. Neoplastic cells were strongly immunoreactive for CD99 and vimentin and were negative for chromogranin, synaptophysin, CD31, CD34, calcitonin, desmin, low-molecular weight cytokeratins, wide-spectrum cytokeratins, leukocyte common antigen, S-100 protein, and thyroid transcription factor-1. The neoplasm was diagnosed as a Ewing's sarcoma/primitive neuroectodermal tumor, and cytogenetic studies confirmed a t(11;22)(q24;q12) chromosomal translocation and an associated trisomy of chromosome 2, supporting the histologic diagnosis. Extraskeletal Ewing's sarcoma/primitive neuroectodermal tumors are rare neoplasms that should be distinguished from other small round-cell tumors by morphology and ancillary laboratory techniques. Although rare, they need to be considered in the differential diagnosis of primary mediastinal tumors.

Terrier-Lacombe MJ, Guillou L, Chibon F, et al.
Superficial primitive Ewing's sarcoma: a clinicopathologic and molecular cytogenetic analysis of 14 cases.
Mod Pathol. 2009; 22(1):87-94 [PubMed] Related Publications
Superficial primitive Ewing's sarcomas are rare and have been reported to be of favorable prognosis compared to conventional deep-seated tumors. In the skin and subcutis, the diagnosis is often difficult, and performing molecular cytogenetic techniques may be helpful. We performed a retrospective analysis of 14 cases of superficial Ewing's sarcomas, all confirmed by molecular cytogenetics. Clinical, histological, immunohistochemical, molecular cytogenetic, therapeutic, and follow-up data are reported. There were 11 female and 3 male patients aged from 12 to 77 years (median: 17 years). Seven tumors occurred in the extremities, five in the trunk wall, and two in the head. Tumor size ranged from 1 to 5 cm (median, 3 cm). They were all small round-cell proliferations with a strong membranous positivity for CD99. Ewing's sarcoma translocations/fusion gene transcripts were detected in eight cases, both by FISH and reverse transcriptase (RT)-PCR. Four tumors were positive by RT-PCR alone (FISH not done in three cases and not interpretable in one case), and two cases were positive by FISH alone (RT-PCR not done). Surgical resection was performed in all patients. Chemotherapy was given in ten patients and radiotherapy in six. At last medical examination (median follow-up, 47 months), two patients who underwent surgical resection alone had died from the tumor. Our results confirm that superficial Ewing's sarcomas are of good prognosis. Given the difficulty of the diagnosis and the importance of an adapted treatment, a confirmation of the diagnosis by molecular or cytogenetic techniques is recommended when dealing with a superficial tumor.

Wang H, Zheng J, Wang YP, et al.
Molecular detection of EWS-Ets fusion transcripts and their clinicopathologic significance in Ewing's sarcoma/peripheral primitive neuroectodermal tumor.
Chin Med J (Engl). 2005; 118(16):1323-9 [PubMed] Related Publications
BACKGROUND: Ewing's sarcoma/peripheral primitive neuroectodermal tumor (ES/pPNET) is often difficult to distinguish from other small round cell tumors. The EWS-Ets gene fusions that result from chromosomal translocations in this tumor provide potential molecular diagnostic markers. To apply these molecular markers to commonly available archival materials, we evaluated the feasibility of detecting EWS-Ets including EWS-Fli1 and EWS-ERG fusion transcripts in paraffin-embedded tissues and its diagnostic value for detecting ES/pPNET.
METHODS: Thirteen paraffin-embedded samples of ES/pPNETs were retrieved from archives. Thirteen cases of other tumors with small round cell features (including rhabdomyosarcoma, neuroblastoma, lymphoma, small cell carcinoma, and desmoplastic small round cell tumor) were used as negative controls. Beta-actin and beta2-microglobulin were used as internal controls. A nested reverse transcriptase-polymerase chain reaction (RT-PCR)-based assay was performed to detect the EWS-Fli1 and EWS-ERG fusion transcripts.
RESULTS: Beta-actin and beta2-microglobulin were detected in 10/13 and 13/13 ES/pPNETs, respectively. EWS-Fli1 fusion transcripts were detected in 11 of 13 (85%) ES/pPNETs. Three chimeric transcripts, all EWS-Fli1, were detected in ES/pPNET samples. Among 11 EWS-Fli1-positive cases, 7 cases had a type I fusion transcript involving fusion of EWS exon 7 with Fli1 exon 6, 2 cases had a type II fusion transcript involving EWS exon 7 with Fli1 exon 5, and 2 cases expressed fusion transcripts involving EWS exon 7 and Fli1 exon 8. Type I EWS-Fli1 fusion predominated over other types. Fusion types could not be distinguished in the remaining 2 cases. Thirteen negative controls did not show detectable chimeric messages. There was a significant relationship between EWS-Fli1 fusion transcripts and CD99 expression.
CONCLUSIONS: Molecular detection of EWS-Fli1 fusion transcripts in formalin-fixed paraffin-embedded material by nested RT-PCR is feasible and is useful for the diagnosis and differential diagnosis of ES/pPNETs.

Khoury JD
Ewing sarcoma family of tumors.
Adv Anat Pathol. 2005; 12(4):212-20 [PubMed] Related Publications
The Ewing sarcoma family of tumors (ESFT) comprises morphologically heterogeneous tumors that are characterized by nonrandom chromosomal translocations involving the EWS gene and one of several members of the ETS family of transcription factors. The translocation t(11;22)(q24;q12) is the most common and leads to the formation of the EWS-FLI1 fusion protein, which contributes to ESFT pathogenesis by modulating the expression of target genes. Tumors may be composed of small uniform cells with minimal morphologic evidence of differentiation, or they may be composed of larger, less uniform cells with varying degrees of neuroectodermal differentiation. CD99 expression is identified in nearly all ESFT and constitutes a useful positive marker when used as part of a panel of immunostains that can help rule out other differential diagnostic considerations. Molecular diagnostic tests commonly used to detect the presence of ESFT-specific translocations include RT-PCR and fluorescence in situ hybridization. Current therapy for patients with ESFT includes chemotherapy and surgery with or without radiation therapy. At present, the most significant prognostic factor for patients with ESFT is whether the disease is localized or metastatic.

Bismar TA, Basturk O, Gerald WL, et al.
Desmoplastic small cell tumor in the pancreas.
Am J Surg Pathol. 2004; 28(6):808-12 [PubMed] Related Publications
Desmoplastic small cell tumor (DSCT) is a distinct type of small blue cell tumors and is characterized by the unique karyotypic aberration involving the fusion of the Ewing's sarcoma (EWS) gene and Wilms' tumor (WT1) gene. Typically, it grows along serosal surfaces; however, in some cases, the tumor presents as a dominant mass in an internal organ. Examples of DSCT forming a primary mass in ovary, testes, and brain have been described, but its presentation as a primary pancreatic mass has not been reported previously. The case reported here is a 31-year-old woman who presented with a 14-cm mass in the pancreas. There were smaller nodules on the peritoneal surfaces that were regarded clinically as metastasis from a primary pancreatic tumor. During the frozen section, the diagnosis of a poorly differentiated endocrine carcinoma of pancreatic origin was rendered and patient underwent subtotal pancreatectomy. On microscopic examination, the tumor was composed of large nests and broad bands of small blue cells, separated by fibrous stroma. Immunohistochemical stains showed positivity of the tumor cells for cytokeratins (AE1:AE3 and CAM5.2), neuron specific enolase, desmin and WT1, whereas chromogranin, S-100, and CD99 were negative. Since this immunoprofile is characteristic of DSCT, molecular analysis was performed which revealed the presence of EWS-WT1 gene fusion characteristic of DSCT. This case shows that in addition to primary pancreatic tumors characterized by prominent cellularity such as solid pseudopapillary tumors, acinar cell carcinoma, pancreatoblastoma, endocrine tumors, and other small blue cell tumors, the differential diagnosis of cellular, stroma-poor neoplasia in the pancreas also includes DSCT. This case is also another demonstrative example of how DSCT may form a dominant mass in intraabdominal organs.

Latest Publications: CD99 (cancer-related)

Cardoso LC, Soares RDS, Laurentino TS, et al.
CD99 Expression in Glioblastoma Molecular Subtypes and Role in Migration and Invasion.
Int J Mol Sci. 2019; 20(5) [PubMed] Free Access to Full Article Related Publications
Glioblastoma (GBM) is the most aggressive type of brain tumor, with an overall survival of 17 months under the current standard of care therapy. CD99, an over-expressed transmembrane protein in several malignancies, has been considered a potential target for immunotherapy. To further understand this potentiality, we analyzed the differential expression of its two isoforms in human astrocytoma specimens, and the CD99 involved signaling pathways in glioma model U87MG cell line. CD99 was also analyzed in GBM molecular subtypes. Whole transcriptomes by RNA-Seq of

Tang S, Dodd LG
CIC-DUX4 sarcoma diagnosed by fine-needle aspiration cytology: A case report.
Diagn Cytopathol. 2018; 46(11):958-963 [PubMed] Related Publications
The CIC-DUX4 sarcoma is a small round blue cell sarcoma which presents like extraskeletal Ewing sarcoma, but is negative for the EWSR1 gene translocation. The recognition of CIC-DUX4 sarcomas as an aggressive sarcoma may be challenging in fine needle aspirates or small needle core biopsies. We present a case of a 13-year-old female with a fine needle aspiration (FNA) and core needle biopsy (CNB) of a thigh mass showing CIC-DUX4 sarcoma. Cytologic findings include tumor cells with high nuclear to cytoplasmic (N:C) ratio, eccentric nuclei and small nucleoli. The tumor cells were arranged in sheets and singly dispersed with background necrosis. Mitotic figures and apoptosis were present. These findings are similar to cases previously reported. Other reported findings of spindled nuclei, clear cell change and lobular growth pattern were not seen in our case. Immunohistochemical stains showed tumor cells positive for CD99, WT1, vimentin and negative for pancytokeratin, desmin and myogenin, which is the pattern similar to cases previously reported. However, our case was also positive for BCL-2. Fluorescence in situ hybridization (FISH) was negative for EWSR1 and SS18 (SYT) rearrangements and positive for CIC gene rearrangement. On balance, if the following features are seen: (1) a small round blue cell tumor with histomorphology more atypical than that of Ewing sarcoma, (2) cytoplasmic CD99 staining, nuclear WT1 positivity, negative keratin, desmin and myogenin; and (3) EWSR1 rearrangement negative by FISH, then molecular testing for CIC-DUX4 sarcoma should be considered.

Louati S, Senhaji N, Chbani L, Bennis S
Dis Markers. 2018; 2018:7971019 [PubMed] Free Access to Full Article Related Publications
Ewing sarcoma/primitive neuroectodermal tumor (Ewing/PNET sarcomas or EPS) are a group of round cell tumors. Malignant round cell tumors form a large and diverse group that includes rhabdomyosarcoma, synovial sarcoma, non-Hodgkin's lymphoma, neuroblastoma, hepatoblastoma, Wilm's tumor, desmoplastic small round cell tumor, and other morphologically similar entities. Differential diagnosis of Ewing sarcoma/primitive neuroectodermal tumor (Ewing/PNET sarcomas or EPS) is difficult. In addition to morphology and immunohistochemistry (IHC), differential diagnosis of these tumors is based on molecular analysis of the

Schaefer IM, Dal Cin P, Landry LM, et al.
CIC-NUTM1 fusion: A case which expands the spectrum of NUT-rearranged epithelioid malignancies.
Genes Chromosomes Cancer. 2018; 57(9):446-451 [PubMed] Related Publications
NUT carcinoma (NC) shows very aggressive clinical behavior, occurs predominantly in the thorax and head and neck region of children and adults, and is defined by the presence of NUT (aka NUTM1) rearrangement, mostly BRD4-NUTM1 fusion resulting from t(15;19)(q13; p13.1). So-called "NUT variants" harbor alternate fusions between NUTM1 and BRD3, NSD3, ZNF532, or unknown partners. Rare cases of pediatric tumors with CIC-NUTM1 fusion were recently reported in somatic soft tissue, brain, and kidney. However, such cases have not been identified in adult patients and the presence of a fusion between CIC, characteristic of CIC-rearranged sarcoma, and NUTM1-a defining feature of NC-poses a diagnostic challenge. We herein report a case of malignant epithelioid neoplasm with myoepithelial features harboring CIC-NUTM1 fusion arising in soft tissue of the head in a 60-year-old man. Immunohistochemistry revealed strong expression of NUT, but only weak ETV4 staining and negativity for keratins, EMA, p40, CD99, and WT1. SMARCB1 expression was retained. Fluorescence in situ hybridization and targeted next-generation sequencing identified a CIC-NUTM1 fusion resulting from t(15;19)(q14;q13.2). In light of morphologic features that overlap with those of NC from typical anatomical sites we have seen previously, the tumor was best classified as falling within the NC spectrum rather than CIC-associated sarcoma. This case highlights the emerging diagnostic challenges generated by newly detected gene fusions of unknown clinical and biologic significance. Careful integration of cytogenetic, molecular, and immunohistochemical findings with morphologic appearances in the diagnostic workup of undifferentiated neoplasms is essential.

Liao YS, Chiang IH, Gao HW
A mesenteric primary peripheral Ewing's sarcoma/primitive neuroectodermal tumor with molecular cytogenetic analysis: Report of a rare case and review of literature.
Indian J Pathol Microbiol. 2018 Apr-Jun; 61(2):248-251 [PubMed] Related Publications
Rare cases of Ewing's sarcoma/primitive neuroectodermal tumors (EWS/PNETs) arising from mesenteric tissue have been reported. This report describes an EWS/PNET in a 25-year-old woman who presented with abdominal pain lasting 3 days. Radiologic evaluation revealed a 9 cm × 6 cm homogeneous mass in the lower abdomen with homogeneous enhancement and invasion of the ileum. Surgical resection was completed during exploratory laparotomy. Immunohistochemically, the tumor cells revealed CD99, friend leukemia virus integration-1 and NKX2.2 (NK2 Homeobox 2, a protein coding gene) and subsequently showed EWSR1 rearrangement. The histological feature, immunohistochemical results and genetic fluorescence in situ hybridization analysis of this case were confirming the diagnosis of EWS/PNET. Adjuvant chemotherapy was suggested, but the patient was lost to follow-up.

Komforti MK, Sokolovskaya E, D'Agostino CA, et al.
Extra-osseous Ewing sarcoma of the pancreas: case report with radiologic, pathologic, and molecular correlation, and brief review of the literature.
Virchows Arch. 2018; 473(3):361-369 [PubMed] Related Publications
In 2002, due to extensive histomorphologic, immunohistochemical, and cytogenetic similarities, the World Health Organization unified undifferentiated small round blue cell neoplasms of soft tissue and bone (previously segregated as Ewing sarcoma or Primitive Neuroectodermal tumor) into one category: Ewing family of tumors (EFT). Osseous EFT are more common, and while extra-osseous EFT can occur anywhere in the body, those of the pancreas are rare and likely to be seen in the second decade of life in the head of the pancreas. We report the case of a 39-year-old Caucasian male with a large heterogeneously enhancing mass in the pancreatic body. Pathologic examination showed a malignant round blue cell tumor diffusely positive for CD99, chromogranin, and synaptophysin; Ki-67 proliferation index was greater than 80%. FISH showed EWSR1 gene rearrangement in 90% of cells and Archer FusionPlexTM-targeted RNA sequencing analysis identified the EWSR1-FLI1 fusion transcript. The diagnosis of EFT of the pancreas was rendered. Unfortunately, the patient had minimal improvement and was transitioned to oral pain medications to continue care at a different institution.

Li J, Zhang W, Wang W, et al.
Forty-nine cases of acute lymphoblastic leukaemia/lymphoma in pleural and pericardial effusions: A cytological-histological correlation.
Cytopathology. 2018; 29(2):172-178 [PubMed] Related Publications
INTRODUCTION: Acute lymphoblastic leukaemia/lymphoma (ALL/LBL) is an aggressive entity of precursor lymphoid neoplasm and may cause malignant serous effusion (SE). The current study aimed to analyse the characteristics of SE cytology of ALL/LBL including cytomorphology, immunophenotyping, clonality and evaluate the effectiveness of SE cytology as a diagnostic method for ALL/LBL.
METHODS: SE specimens with final diagnosis of ALL/LBL from 2006 to 2016 were reviewed for clinical data, cytomorphological features and ancillary studies. Cytodiagnoses were compared with histodiagnoses, and the discordant cases were analysed.
RESULTS: A total of 49 specimens including 47 pleural fluids and 2 pericardial fluids from 49 patients were evaluated. Cytomorphology revealed lymphoblasts varied from small size with scant cytoplasm, condensed nuclear chromatin and indistinct nucleoli to large size with dispersed nuclear chromatin and multiple variably prominent nucleoli. Nuclear clefts and hand mirror-shaped blasts were demonstrated. The positive rates of CD99 and terminal deoxynucleotidyl transferase were 90.9% and 81.6%, respectively. Both monoclonal immunoglobulin (Ig)H and T-cell receptor-γ gene rearrangements were demonstrated in 1 of 3 cases. Monoclonal T-cell receptor-γ gene rearrangement was found in 10 of 11 cases. Monoclonal IgH and/or Ig? gene rearrangements were revealed in 2 of 3 cases. Cytodiagnoses included 4 ALL/LBL, 3 B-ALL/LBL and 42 T-ALL/LBL. Histodiagnoses were available in 24 cases including 2 ALL/LBL, 2 B-ALL/LBL and 20 T-ALL/LBL. The concordance rates of cytological-histological diagnoses were 66.7%, 0% and 95.2% in the three categories, respectively. There were 3 cases with discrepancies of cell lineages.
CONCLUSIONS: SE cytological evaluation is a reliable and effective method for the diagnosis of ALL/LBL.

Koelsche C, Hartmann W, Schrimpf D, et al.
Array-based DNA-methylation profiling in sarcomas with small blue round cell histology provides valuable diagnostic information.
Mod Pathol. 2018; 31(8):1246-1256 [PubMed] Related Publications
Undifferentiated solid tumors with small blue round cell histology and expression of CD99 mostly resemble Ewing sarcoma. However, they also may include other tumors such as mesenchymal chondrosarcoma, synovial sarcoma, or small cell osteosarcoma. Definitive classification usually requires detection of entity-specific mutations. While this approach identifies the majority of Ewing sarcomas, a subset of lesions remains unclassified and, therefore, has been termed "Ewing-like sarcomas" or small blue round cell tumors not otherwise specified. We developed an approach for further characterization of small blue round cell tumors not otherwise specified using an array-based DNA-methylation profiling approach. Data were analyzed by unsupervised clustering and t-distributed stochastic neighbor embedding analysis and compared with a reference methylation data set of 460 well-characterized prototypical sarcomas encompassing 18 subtypes. Verification was performed by additional FISH analyses, RNA sequencing from formalin-fixed paraffin-embedded material or immunohistochemical marker analyses. In a cohort of more than 1,000 tumors assumed to represent Ewing sarcomas, 30 failed to exhibit the typical EWS translocation. These tumors were subjected to methylation profiling and could be assigned to Ewing sarcoma in 14 (47%), to small blue round cell tumors with CIC alteration in 6 (20%), to small blue round cell tumors with BCOR alteration in 4 (13%), to synovial sarcoma and to malignant rhabdoid tumor in 2 cases each. One single case each was allotted to mesenchymal chondrosarcoma and adamantinoma. 12/14 tumors classified as Ewing sarcoma could be verified by demonstrating either a canonical EWS translocation evading initial testing, by identifying rare breakpoints or fusion partners. The methylation-based assignment of the remaining small blue round cell tumors not otherwise specified also could be verified by entity-specific molecular alterations in 13/16 cases. In conclusion, array-based DNA-methylation analysis of undifferentiated tumors with small blue round cell histology is a powerful tool for precisely classifying this diagnostically challenging tumor group.

Zhang Y, Wan D, Gao F
Primary low-grade fibromyxoid sarcoma of the breast: a rare case report with immunohistochemical and fluorescence in situ hybridization detection.
Hum Pathol. 2018; 79:208-211 [PubMed] Related Publications
Low-grade fibromyxoid sarcoma (LGFMS) is a rare tumor with a bland histologic appearance but malignant biological behavior. Primary LGFMS of the breast has not been described in the English-language literature. Here, we report a 58-year-old Chinese female patient who presented with a painless mass in the right breast for more than 30 years. The tumor consists of spindle cells resembling fibroblasts and includes 2 kinds of morphologic change, which are alternating collagenized hypocellular zone and cell-rich myxoid area. There are more arcades of curvilinear blood vessels. The spindle cells are not heteromorphic, and mitotic figures are scarce. Immunostaining shows that tumor cells are positive for vimentin, mucin4, CD99, and Bcl-2, but negative for smooth muscle actin, desmin, S100, CD34, ALK, and myogenin. FUS gene rearrangement is positively detected by fluorescence in situ hybridization. The patient has been followed up for 59 months and is in a favorable condition. This rare location of LGFMS should be noted.

He XR, Liu Z, Wei J, et al.
Primary desmoplastic small round cell tumor in the left orbit: a case report and literature review.
Int Ophthalmol. 2019; 39(2):471-475 [PubMed] Related Publications
PURPOSE: Desmoplastic small round cell tumor is a rare malignant neoplasm that most often occurs in the abdomen or pelvis of young men. We herein describe a rare case of desmoplastic small round cell tumor arising from the left orbit in a 16-year-old male.
METHODS AND RESULTS: A biopsy was performed and the histology showed the nests of tumor cells with small round cell morphology. The tumor cells showed immunopositivity for desmin, CD99, CD56, SMA, NSE, CgA, SYN, Ki67 and vimentin. Fluorescence in situ hybridization study using EWSR1 break-apart probe was positive for EWSR1 gene rearrangement. After complete surgical resection of the tumor, we did not find tumor recurrence or metastasis with one-year follow-up. Furthermore, a review of the relevant English literature has been discussed.
CONCLUSIONS: In the present study, for the first time, we report a case of desmoplastic small round cell tumor which is located in the orbital region.

Zhao XY, Zeng M, Yang QY, et al.
Scrotum solitary fibrous tumor: A case report and review of literature.
Medicine (Baltimore). 2017; 96(48):e8854 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: A solitary fibrous tumor (SFT) is a rare clinical tumor, often manifesting as solitary nodules. It is a rare condition that occurs in the scrotum. Currently, no study has reported this condition.
CASE SUMMARY: We reported a case of an SFT in a 77-year-old man, and discuss its diagnosis, differential diagnosis, and treatment. Clinical and histopathological features, as well as the EnVision 2-step method, were used to diagnosis the SFT. The results of imaging tests and surgery indicated that the SFT was located in the right scrotum with 2 connected tumor nodules and a clear perimeter. The larger one was 11.0 cm × 9.3 cm × 8.1 cm, and the smaller one was 3.1 cm × 2.0 cm × 2.0 cm. Pathological results indicated that in both tumor nodules, tumor cells were spindle-shaped with unclear cell boundaries. The nucleus was vacuolated with mild to moderate atypia. In the larger tumor nodule, there were many thin-walled blood vessels with vasodilation or branching. In the smaller tumor nodule, rich blood vessels were found, mostly with fibrous degeneration of the thick walls of blood vessels, and more collagen-like tissue in the interstitial layers. Immunohistochemical results demonstrated diffuse, strongly positive expression of CD34, CD99, Vim, and Bcl-2 markers. The expression of the new fusion gene, NAB2-STAT6, as an alternative tool specifically confirmed the diagnosis of SFT. This patient underwent lump resection without further treatment. The patient is alive after 18-month follow-up.
CONCLUSION: This case was diagnosed as a SFT according to its histopathological features, immunophenotype. The patient is still alive at 18 months follow-up after the lump resection.

Lilo MT, Bishop JA, Olson MT, Ali SZ
Adamantinoma-like Ewing sarcoma of the parotid gland: Cytopathologic findings and differential diagnosis.
Diagn Cytopathol. 2018; 46(3):263-266 [PubMed] Related Publications
Adamantinoma-like Ewing sarcoma (AES) is a rare variant of Ewing sarcoma family of tumors (EFTs), primarily affecting bone and soft tissue. AES has mixed features of Ewing sarcoma (ES)/primitive neuroectodermal tumor (PNET) and adamantinoma with a complex immunoprofile and EWSR1 gene rearrangements. Herein, we report a 72-year-old male who presented with left parotid mass, right neck mass and thyroid nodules. Fine needle aspiration of the left parotid mass displayed nests of monotonous epithelioid cells with basaloid features in a background of small round blue cells and lymphocytes. AES can involve head and neck region and is characterized by groups of primitive small round blue cells admixed with groups of epithelioid cells with amphophilic cytoplasm and focal squamous differentiation. The proportion of these components can be variable, creating diagnostic challenges, particularly in unusual anatomic sites such as the parotid gland. However, when additional material is available, CD99 and/or FLI1 immunostains need to be included for diagnostic confirmation.

Matsuyama A, Shiba E, Umekita Y, et al.
Clinicopathologic Diversity of Undifferentiated Sarcoma With BCOR-CCNB3 Fusion: Analysis of 11 Cases With a Reappraisal of the Utility of Immunohistochemistry for BCOR and CCNB3.
Am J Surg Pathol. 2017; 41(12):1713-1721 [PubMed] Related Publications
Undifferentiated sarcoma harboring the BCOR-CCNB3 fusion is characterized by its predilection to affect skeletons of adolescent males, cellular small round/spindle cell morphology, and CCNB3 immunoreactivity. We analyzed 11 cases of BCOR-CCNB3 sarcoma, 10 of which were identified in a reverse transcription-polymerase chain reaction-based screen of 85 patient samples recorded in our database as unclassified small round or spindle cell sarcomas. BCOR rearrangements were confirmed by fluorescence in situ hybridization in 8 tumors. All patients were males aged between 6 and 31 years. In addition to 5 tumors in soft tissue and 4 in the axial or appendicular skeletons, which are typical locations, a tumor was located in the paranasal sinus and another in the lung. Microscopically, the tumors comprised proliferating atypical spindle and/or small round cells with diverse morphologic features such as small concentric whorls, myxoid stroma, a hemangiopericytomatous appearance, and/or hyalinized collagen resembling a solitary fibrous tumor, and angiomatous or slit-like spaces containing extravasated erythrocytes. Tumor cells were immunoreactive to CCNB3 (9/11), BCOR (10/10), TLE1 (6/10), bcl-2 (9/11), CD99 (8/10), CD56 (8/10), c-kit (4/10), and cyclin D1 (10/10). In an immunohistochemical analysis of an additional 412 small round or spindle cell tumors, CCNB3 was detected in 6 (1.5%) and BCOR in 18 (4.4%). Our analysis highlights the varying clinicopathologic features of this tumor, which partially overlap with other small round or spindle cell tumors, including solitary fibrous tumor and vascular tumors. Because CCNB3 and BCOR immunohistochemistry lacks adequate sensitivity and specificity, a molecular genetic approach remains essential for diagnosis.

Machado I, Yoshida A, López-Guerrero JA, et al.
Immunohistochemical analysis of NKX2.2, ETV4, and BCOR in a large series of genetically confirmed Ewing sarcoma family of tumors.
Pathol Res Pract. 2017; 213(9):1048-1053 [PubMed] Related Publications
Ewing sarcoma is an aggressive neoplasm of pediatric and adolescent patients. Immunohistochemistry (IHC) can be used to support the morphologic diagnosis of Ewing sarcoma family of tumors (ESFT) in a convincing clinical/radiological context. Although neither NKX2.2 nor CD99 alone are entirely specific, when combined, the diagnostic specificity is high. The aim of the present study was to investigate the IHC expression of NKX2.2, ETV4 and BCOR in a large series of genetically confirmed ESFT. The results for CD99 and CAV-1 immunoreactivity, and the histological and fusion gene subtypes were retrieved from our previous study. NKX2.2 demonstrated moderate or strong nuclear positivity in 91.2% of the tumors. The staining intensity was heterogeneous. Many of the ESFT with negative NKX2.2 immunoreactivity were in bone. Strong/moderate ETV4 nuclear expression was detected in two small round cell tumors, both were negative for NKX2.2. No relationships could be found between expression of NKX2.2 and the histological subgroups or ESFT gene fusion subtypes. BCOR was negative in all ESFT. In conclusion, NKX2.2, ETV4 and BCOR IHC may be helpful in daily practice for distinguishing ESFT from CIC or BCOR-associated sarcomas, especially in hospitals without access to molecular assays. In addition, the combination of strong CD99 membranous positivity and nuclear NKX2.2 positivity seems to be very reliable for ESFT diagnosis in an appropriate clinicoradiological setting. So far no antibody is entirely specific for ESFT diagnosis, and the IHC or molecular results in round cell tumors of bone may be strongly influenced by decalcification processes.

Schifflers S, Delbecque K, Galant C, et al.
Microscopic Infiltration of Cryopreserved Ovarian Tissue in 2 Patients With Ewing Sarcoma.
J Pediatr Hematol Oncol. 2018; 40(3):e167-e170 [PubMed] Related Publications
We report the clinical history of 2 female patients with Ewing sarcoma and microscopic ovarian infiltration. In both cases, the initial workup found no metastasis. However, the examination of cryopreserved ovarian tissues revealed the presence of CD99 positive tumor cells with rearrangement of EWS gene confirmed by FISH. Both children were treated as patients with localized tumor and are currently in remission. These reports underline that, in Ewing sarcoma patients, retransplantation of cryopreserved ovarian tissue is not harmless and could lead to cancer relapse. These observations question also on the significance of ovarian dissemination on Ewing sarcoma prognosis and therapy.

Jiang D, Peng R, Yan X, et al.
Synovial sarcoma showing loss of a green signal in SS18 fluorescence in situ hybridization: a clinicopathological and molecular study of 12 cases.
Virchows Arch. 2017; 471(6):799-807 [PubMed] Related Publications
The phenomenon of losing a green signal in synovial sarcoma (SS) using the SS18 break-apart probe by fluorescence in situ hybridization (FISH) has been poorly described. In this study, 12 SS with missing a green signal were identified. This series included 7 males and 5 females, aged 17 to 69 years (median, 38.5 years). The tumors involved the extremities (50%), mediastinum (16.7%), hypopharynx (8.3%), neck (8.3%), thyroid (8.3%), and retroperitoneum (8.3%). The tumors were classified as monophasic SS (58.3%) and poorly differentiated SS (41.7%). An anaplastic SS showing features of pleomorphic sarcoma was observed. Immunostaining for TLE1, BCL2, CD99, epithelial membrane antigen, cytokeratin (AE1/AE3), cytokeratin 7, S-100 protein, and CD34 was consistent with typical SS. In FISH, all the tumors showed the pattern of 1 to 3 fused signal(s) with 1 to 3 red signal(s), without corresponding a green signal. The fusion transcripts included SS18-SSX1 (8/10, 80%) and SS18-SSX2 (2/10, 20%) fusions. Median and 5-year overall survival were 19.1 months and 43.6%, respectively. In conclusion, we reported a series of SS losing a green signal in the SS18 FISH assay. We propose that this variant FISH pattern should be interpreted as a peculiar unbalanced rearrangement of the SS18 gene and subsequent SS18-SSX fusion test should be recommended. The cases in this study seem to show some unusual clinicopathological features, including unusual locations, higher proportions of poorly differentiated SS, and aggressive clinical course. However, whether this variant FISH pattern is associated with peculiar clinicopathologic features awaits larger series.

Alfaro-Cervello C, Andrade-Gamarra V, Nieto G, et al.
Congenital undifferentiated sarcoma associated to BCOR-CCNB3 gene fusion.
Pathol Res Pract. 2017; 213(11):1435-1439 [PubMed] Related Publications
Small round cell sarcomas are aggressive bone and soft tissue tumors that predominantly affect children and young adults. A new group of sarcomas with a recurrent BCOR-CCNB3 gene fusion has been recently identified in previously unclassifiable small round cell sarcomas. BCOR-CCNB3 sarcomas share clinical and pathologic similarities with Ewing sarcoma, but show a stronger male predilection and less aggressiveness, as well as distinct gene expression profiling and pangenomic SNP array analyses. We report the unusual case of a congenital BCOR-CCNB3 retroperitoneal sarcoma in a female born at 34th gestational week, which was diagnosed in necropsy after 21hours of life. Immunohistochemical analysis showed diffuse expression of CD99 and CCNB3. SNPa showed two focal segmentary deletions at 5q34 and 22q11.23, the latter harboring among others the SMARCB1/INI1 tumor suppressor gene. Immunohistochemistry confirmed loss of INI1 in tumor cells, which has not been previously reported in this type of undifferentiated sarcomas.

Tsukamoto Y, Futani H, Yoshiya S, et al.
Primary undifferentiated small round cell sarcoma of the deep abdominal wall with a novel variant of t(10;19) CIC-DUX4 gene fusion.
Pathol Res Pract. 2017; 213(10):1315-1321 [PubMed] Related Publications
We experienced a 38-year-old Japanese male with t(10;19) CIC-DUX4 -positive undifferentiated small round cell sarcoma in the deep abdominal wall. Three months before his first visit to our hospital, he noticed a mass in his right abdominal wall. Computed tomography on admission revealed a solid abdominal tumor 70×53mm in size and multiple small tumors in both lungs. The biopsy of the abdominal tumor revealed undifferentiated small round cell sarcoma, suggestive of Ewing sarcoma. Under the clinical diagnosis of Ewing-like sarcoma of the abdominal wall with multiple lung metastases, several cycles of ICE (ifosfamide, carboplatin and etoposide) therapy were performed. After the chemotherapy, the lung metastases disappeared, while the primary lesion rapidly grew. Additional VDC (vincristine, doxorubicin and cyclophosphamide) therapy was carried out without apparent effect. Although the surgical removal of the primary lesion was done, peritoneal dissemination and a huge metastatic liver tumor appeared thereafter. The patient died of disease progression two months after the surgery. The total clinical course was approximately one year, showing that the tumor was extremely aggressive. The tumor cells of the surgical specimen were positive for CD99, WT1, calretinin, INI1, ERG and Fli1 by immunohistochemistry. Fusion gene analyses using the frozen surgical material revealed negativity for EWSR1-Fli1, EWSR1-ERG and t(4;19) CIC-DUX4 fusions, but positivity for t(10;19) CIC-DUX4 fusion. Thus, we made a final pathological diagnosis of t(10;19) CIC-DUX4-positive undifferentiated small round cell sarcoma. To our knowledge, this is the 13th case of t(10;19) CIC-DUX4 undifferentiated small round cell sarcoma with precise clinicopathological information. Especially in our case, two types of t(10;19) CIC-DUX4 fusion transcripts were observed, both of which are in-frame and novel.

Li T, Zhang F, Cao Y, et al.
Primary Ewing's sarcoma/primitive neuroectodermal tumor of the ileum: case report of a 16-year-old Chinese female and literature review.
Diagn Pathol. 2017; 12(1):37 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Ewing's sarcoma (ES) and primitive neuroectodermal tumors (PNET) are closely related tumors. Although soft tissue ES/PNET are common in clinical practice, they are rare in the small intestine. Because of the absence of characteristic clinical symptoms, they are easily misdiagnosed as other benign or malignant diseases.
CASE PRESENTATION: Here, we present the case of a 16-year-old female who complained of anemia and interval hematochezia. Her serum test results showed only a slight elevation of CA-125 and a low level of hemoglobin. Computer tomography and magnetic resonance imaging revealed a cystic and solid mass in the lower abdominal quadrant and pelvic region, which prompted suspicion of a malignant gastrointestinal stromal tumor of the small intestine. After resection, the tumor's histology and immunohistochemistry (positive for CD99, vimentin and synaptophysin) results suggested ES/PNET. Fluorescent in situ hybridization tests proved the breakpoint rearrangement of the EWSR1 gene in chr 22.Ultrastructural analysis revealed neurosecretory and glycogen granules in the tumor cell cytoplasm.
CONCLUSIONS: Together, these data supported the diagnosis of a rare case of localized ES/PNET in the small intestine without adjuvant chemo- or radiotherapy. To our knowledge, this is the first report from China of a primary small bowel ES/PNET in the English-language literature. In addition, on the basis of findings from previous publications and the current case, the optimal treatment for localized gastrointestinal ES/PNET is discussed.

Hue SS, Iyer P, Toh LHW, et al.
Primary Bone Anaplastic Large Cell Lymphoma Masquerading as Ewing Sarcoma: Diagnosis by Anchored Multiplex PCR.
J Pediatr Hematol Oncol. 2018; 40(2):e103-e107 [PubMed] Related Publications
A 3-year-old boy presented with pathologic fracture of the left proximal femur. Magnetic resonance imaging revealed an aggressive expansile bony mass associated with cortical destruction and surrounding myositis. Computed tomography-guided biopsy revealed a monomorphic small round blue cell tumor by histology. CD99 immunoreactivity and low-level EWSR1 gene translocation by break-apart fluorescent in situ hybridization initially favored a diagnosis of Ewing sarcoma and chemotherapy commenced. Subsequent molecular evaluation by an anchored multiplex polymerase chain reaction-based assay (Archer FusionPlex Sarcoma Panel) revealed a nucleophosmin-anaplastic lymphoma kinase (NPM-ALK) gene fusion. The diagnosis was then amended to primary bone ALK-positive anaplastic large cell lymphoma and the chemotherapy regimen was modified accordingly. This report illustrates the value of this molecular assay in establishing the correct diagnosis of a very rare malignancy masquerading as another tumor type.

Pacheco MC, Dolan M, Bendel A
Ewing Sarcoma and Atypical Teratoid Rhabdoid Tumor: A FISH and Immunohistochemical Comparison.
Pediatr Dev Pathol. 2017 Sep-Oct; 20(5):381-386 [PubMed] Related Publications
Ewing sarcoma (ES) and atypical teratoid rhabdoid tumor (ATRT) are high-grade malignancies of childhood, each of which is associated with genetic abnormalities on chromosome 22. ES is typically characterized by rearrangement of the EWSR1 locus and ATRT by deletion of SMARCB1. We report a case with an unusual fluorescence in situ hybridization signal pattern consistent with EWSR1 rearrangement that was shown to have loss of INI1 expression by immunohistochemistry due to deletion in the long arm of one chromosome 22. In light of the unusual findings in this case as well as the proximity of the EWSR1 locus and SMARCB1 locus on chromosome 22 and frequent CD99 staining in both tumors, we examined 16 ES cases and 17 ATRT, renal rhabdoid tumor (RRT), and extrarenal rhabdoid tumor (ERRT) cases for CD99 and INI1 staining and for EWSR1 rearrangement. Staining with INI1 was negative in ATRT, RRT, and ERRT and positive in ES cases; CD99 was positive in ES cases and variable in ATRT cases. All but 2 cases of ES, and no cases of ATRT, showed rearrangement of EWSR1. The present case appears to be best classified as a unique variant of ATRT based on immunohistochemistry, EWSR1 fluorescence in situ hybridization and RT-PCR, and SMARCB1 gene sequencing.

Antonescu CR, Owosho AA, Zhang L, et al.
Sarcomas With CIC-rearrangements Are a Distinct Pathologic Entity With Aggressive Outcome: A Clinicopathologic and Molecular Study of 115 Cases.
Am J Surg Pathol. 2017; 41(7):941-949 [PubMed] Free Access to Full Article Related Publications
CIC-DUX4 gene fusion, resulting from either a t(4;19) or t(10;19) translocation, is the most common genetic abnormality detected in EWSR1-negative small blue round cell tumors. Following their discovery it was debated if these tumors should be classified as variants of Ewing sarcoma (ie, atypical Ewing sarcoma) or as a stand-alone pathologic entity. As such the WHO classification temporarily grouped the CIC-rearranged tumors under undifferentiated sarcomas with round cell phenotype, until further clinical evidence was available. However, most studies reported so far include small series with limited follow-up information, which preclude a more definitive assessment. The present work investigates the clinicopathologic features of a large cohort of sarcomas with CIC gene rearrangement, to define their clinical presentation, morphologic spectrum, and outcome. Our study further examines the overall survival of the CIC-positive cohort compared with a control group of EWSR1-rearranged Ewing sarcoma matched for age and stage. The study cohort included 115 patients, with a mean age of 32 years and a slight male predominance. Most tumors occurred in the soft tissue (86%), predominantly deep-seated and equally divided among trunk and extremity, followed by visceral locations (12%) and rarely in the bone (3%). Microscopically, most tumors showed round to ovoid cytomorphology but half of the cases showed also focal areas of spindling and epithelioid/rhabdoid phenotype, with frequent myxoid stromal changes. Variable CD99 reactivity was seen in 84% cases, with a diffuse pattern only in 23% of cases, whereas nuclear WT1 was seen in 92%. A CIC-DUX4 fusion was detected in 57% of cases, with either DUX4 on 4q35 (35%) or on 10q26 in 25 (22%) cases. No FOXO4 gene rearrangements were present in 39 cases tested. Clinical follow-up was available in 57 patients, with a 5-year survival of 43%, which was significantly lower than the 77% 5-year survival in the control Ewing sarcoma group (P=0.002). Our findings show that CIC-DUX4 sarcomas occur most commonly in young adults within the somatic soft tissues, having a wide spectrum of morphology including round, epithelioid and spindle cells, and associated with an aggressive clinical course, with an inferior overall survival compared with Ewing sarcoma. The results support the classification of CIC-rearranged tumors as an independent molecular and clinical subset of small blue round cell tumors distinct from Ewing sarcoma.

Rekhi B, Shetty O, Ramadwar M, et al.
Role of fine needle aspiration cytology in the diagnosis of a rare case of a poorly differentiated synovial sarcoma with "Rhabdoid" features, including treatment implications.
Diagn Cytopathol. 2017; 45(7):662-667 [PubMed] Related Publications
Synovial sarcoma is a high-grade, soft tissue sarcoma that is relatively chemosensitive. Its exact diagnosis is crucial, including differentiation from its closest diagnostic mimic, ie, Ewing sarcoma, in view of different treatment options, including chemotherapy regimens, for both these tumors. A 15-year-old girl presented with a recurrent soft tissue mass in her right popliteal region, which was diagnosed as Ewing sarcoma, based on positive immunoexpression of MIC2/CD99, Fli1 and negative expression of LCA and desmin. During her metastatic "work-up", a popliteal lymph node was identified, which was aspirated and examined. Fine needle aspiration cytology smears showed singly scattered and loose, cohesive clusters of cells containing round to polygonal, to short spindle-shaped nuclei with prominent nuclei, and moderate to abundant cytoplasm, including several "rhabdoid" cells. These features prompted a review of the biopsy of the recurrent tumor, and additional immunohistochemical stains, which revealed positive co-expression of pan cytokeratin (AE1/AE3), epithelial membrane antigen (EMA), along with a characteristic variable staining pattern of INI11/SMARCB1. Subsequently, by fluorescent in situ hybridization (FISH) technique, performed on the paraffin section of the recurrent tumor, 100% tumor nuclei displayed SS18 rearrangement, while none of the tumor cells displayed EWSR1 rearrangement. Diagnosis of poorly differentiated SS with "rhabdoid" features was confirmed. This constitutes as the first case, describing cytopathologic features of a poorly differentiated SS with "rhabdoid" features, initially misdiagnosed as a Ewing sarcoma, on biopsy and confirmed as SS by FISH technique. The diagnostic and treatment implications in this case are discussed herewith. Diagn. Cytopathol. 2017;45:662-667. © 2017 Wiley Periodicals, Inc.

Owosho AA, Estilo CL, Huryn JM, et al.
Head and Neck Round Cell Sarcomas: A Comparative Clinicopathologic Analysis of 2 Molecular Subsets: Ewing and CIC-Rearranged Sarcomas.
Head Neck Pathol. 2017; 11(4):450-459 [PubMed] Free Access to Full Article Related Publications
CIC-rearranged sarcoma (CRS) is a relatively new entity defined by its pathognomonic genetic signature and undifferentiated round cell phenotype, initially grouped together with the 'Ewing sarcoma-like tumors'. However, increasing data suggest that these tumors should be regarded as a stand-alone pathologic entity. We conducted a clinicopathologic analysis on molecularly conformed Ewing sarcoma (ES) and CRS arising in the head and neck (HN) and compared to a well characterized cohort of ES and CRS from other locations. A total of 41 HN round cell sarcoma patients were selected from our institutional and consultation files, including 25 ES (median 20 years) and 16 CRS (median 29 years). Clinical follow-up information was available for all ES patients, ranging from 4 to 436 months (median 70 months), while for CRS, follow-up information was available in 11 patients (69%), ranging from 1 to 269 months (median 27 months). The most common location for ES was the facial and jaw bones (56%), while CRS occurred exclusively in the soft tissue, commonly in the neck. CRS showed variable CD99 staining in 75% of cases and diffuse WT1 (6/6) reactivity, while all ES expressed diffuse membranous staining for CD99 but none for WT1 (0/6). The 2-year overall survival (OS) rate for HN-CRS patients was 78%, while for HN-ES it was 100%. The OS of ES and CRS showed a trend toward a favorable outcome for HN-round cell sarcomas compared to other sites. Our findings suggest that HN-CRS have different clinical presentation and pathologic features compared to ES and should be classified as a stand-alone pathologic entity.

Chiang S, Snuderl M, Kojiro-Sanada S, et al.
Primitive Neuroectodermal Tumors of the Female Genital Tract: A Morphologic, Immunohistochemical, and Molecular Study of 19 Cases.
Am J Surg Pathol. 2017; 41(6):761-772 [PubMed] Free Access to Full Article Related Publications
Primary primitive neuroectodermal tumor (PNET) of the female genital tract is rare, and its proper classification remains unclear. The clinical, histologic, and immunophenotypic features as well as EWSR1 rearrangement status of 19 gynecologic PNETs, including 10 ovarian, 8 uterine, and 1 vulvar tumors, are herein reported. Patient age ranged from 12 to 68 years, with a median age of 20 and 51 years among those with ovarian and uterine PNETs, respectively. Morphologic features of central nervous system (CNS) tumors were seen in 15 PNETs, including 9 medulloblastomas, 3 ependymomas, 2 medulloepitheliomas, and 1 glioblastoma, consistent with central PNET. The remaining 4 PNETs were composed entirely of undifferentiated small round blue cells and were classified as Ewing sarcoma/peripheral PNET. Eight PNETs were associated with another tumor type, including 5 ovarian mature cystic teratomas, 2 endometrial low-grade endometrioid carcinomas, and a uterine carcinosarcoma. By immunohistochemistry, 17 PNETs expressed at least 1 marker of neuronal differentiation, including synaptophysin, NSE, CD56, S100, and chromogranin in 10, 8, 14, 8, and 1 tumors, respectively. GFAP was positive in 4 PNETs, all of which were of central type. Membranous CD99 and nuclear Fli-1 staining was seen in 10 and 16 tumors, respectively, and concurrent expression of both markers was seen in both central and Ewing sarcoma/peripheral PNETs. All tumors expressed vimentin, whereas keratin cocktail (CAM5.2, AE1/AE3) staining was only focally present in 4 PNETs. Fluorescence in situ hybridization was successful in all cases and confirmed EWSR1 rearrangement in 2 of 4 tumors demonstrating morphologic features of Ewing sarcoma/peripheral PNET and concurrent CD99 and Fli-1 expression. In conclusion, central and Ewing sarcoma/peripheral PNETs may be encountered in the female genital tract with central PNETs being more common. Central PNETs show a spectrum of morphologic features that overlaps with CNS tumors but lack EWSR1 rearrangements. GFAP expression supports a morphologic impression of central PNET and is absent in Ewing sarcoma/peripheral PNET. Ewing sarcoma/peripheral PNETs lack morphologic features of CNS tumors.

Bale TA, Oviedo A, Kozakewich H, et al.
Intracranial myxoid mesenchymal tumors with EWSR1-CREB family gene fusions: myxoid variant of angiomatoid fibrous histiocytoma or novel entity?
Brain Pathol. 2018; 28(2):183-191 [PubMed] Related Publications
Intracranial myxoid mesenchymal tumor harboring EWSR1 fusions with CREB family of genes was recently described, and it resembles the myxoid variant of angiomatoid fibrous histiocytoma. We present three pediatric patients with intracranial EWSR1-rearranged myxoid mesenchymal neoplasm and provide a molecular genetic characterization of these tumors. Clinical histories and imaging results were reviewed. Histology, immunohistochemistry, EWSR1, FUS, NR4A3 fluorescence in situ hybridization (FISH), and next-generation sequencing (NGS) were performed. A 12-year-old male (case 1), 14-year-old female (case 2), and 18-year-old male (case 3), presented with headaches, emesis, and seizures, respectively. The magnetic resonance images demonstrated tumors abutting the dura (cases 1 and 3) and in the third ventricle (case 2). All tumors were vascular, with solid sheets of monomorphic oval cells in a prominent myxoid/microcystic matrix. A thin fibrous pseudocapsule was present in all lesions, but definitive lymphocytic cuffing was absent. Morphologically, they closely resembled myxoid variant of angiomatoid fibrous histiocytoma. Mitoses were rare, and necrosis was absent. All tumors expressed desmin and GLUT1, and focal EMA and CD99. The proliferation index was low. FISH and NGS showed EWSR1-CREB1 fusion (cases 1 and 2), and EWSR1-CREM fusion (case 3). There were no FUS (16p11.2) or NR4A3 (9q22.33) rearrangements in case 3. Gains of 5q (including KCNIP1) and 11q (including CCND1) were present in cases 1 and 2. There were no common pathogenic genomic changes other than EWSR1 rearrangements across cases. CNS myxoid mesenchymal neoplasms with histological and immunophenotypic similarities to myxoid variant of AFH are rare, diagnostically challenging, and harbor EWSR1-CREB1 and also a novel EWSR1-CREM fusion not yet described in AFH. Therefore, it is uncertain if these tumors represent variants of AFH or a new entity. The copy number and mutational changes presented here provide support for future studies to further clarify this issue.

Alexiev BA, Tumer Y, Bishop JA
Sinonasal adamantinoma-like Ewing sarcoma: A case report.
Pathol Res Pract. 2017; 213(4):422-426 [PubMed] Related Publications
We describe the case of a sinonasal adamantinoma-like Ewing sarcoma in a 41-year-old male. Histologically, the tumor exhibited distinctive areas of nested growth pattern with prominent stromal fibrosis and metaplastic bone formation. The tumor cells were small and uniform with minimal amount of pale eosinophilic to clear cytoplasm and round or oval nuclei with finely dispersed chromatin and small nucleoli. Approximately 20% of the tumor parenchyma comprised of small clusters of basaloid cells within an osteofibrous background resembling adamantinoma. The tumor showed strong expression of keratins, p63, CD99 and Fli-1, and EWSR1 rearrangement. The diagnosis of sinonasal Ewing family tumors is particularly problematic owing to the large number of potential mimics. For any poorly differentiated or undifferentiated head and neck tumor, cellular monotony and CD99 immunoreactivity should prompt consideration for molecular studies that include analysis of both EWSR1 and FLI1, even in the presence of strong cytokeratin expression or focal keratinization.

Yamada Y, Kuda M, Kohashi K, et al.
Histological and immunohistochemical characteristics of undifferentiated small round cell sarcomas associated with CIC-DUX4 and BCOR-CCNB3 fusion genes.
Virchows Arch. 2017; 470(4):373-380 [PubMed] Related Publications
CIC-DUX4 and BCOR-CCNB3 fusion-gene-associated small round cell sarcomas account for a proportion of pediatric small round cell sarcomas, but their pathological features have not been sufficiently clarified. We reviewed a large number of soft tissue tumors registered at our institution, retrieved the cases of unclassified tumors with a small round cell component, and subjected them to histopathological, immunohistochemical, and gene profile analysis. We reviewed 164 cases of unclassified tumors with a small round cell component and analyzed them by RT-PCR and FISH. Tumors positive for a specific fusion-gene were also subjected to histopathological and immunohistochemical examinations. We identified 16 cases of BCOR-CCNB3/CIC-associated (CIC-DUX4 or CIC gene rearrangement-positive) sarcomas. These included seven BCOR-CCNB3 sarcomas and nine CIC-associated sarcomas. Heterogeneous elements included a myxoid spindle cell component in three BCOR-CCNB3 sarcomas and an epithelioid cell component in two CIC-associated sarcomas (one CIC-DUX4-positive and one CIC-DUX4-negative sarcomas). Mitotic activity was low in both heterogeneous components. By immunohistochemistry, in seven BCOR-CCNB3 sarcomas expression of EMA was positive in two cases, of p63 in three, of CD56 in six, of TLE1 in seven, of NKX2.2 in two, of CCNB3 in seven, and of BCOR in six cases (one case could not be tested for BCOR). In nine cases of CIC-associated sarcoma, CD56 was expressed in five, alpha-smooth muscle actin in one, ERG in three, and CD99, WT1 and TLE1 each in eight cases. Both sarcoma types showed not only a small round cell component, but also a myxoid/epithelioid component with low mitotic activity.

Sugita S, Arai Y, Aoyama T, et al.
NUTM2A-CIC fusion small round cell sarcoma: a genetically distinct variant of CIC-rearranged sarcoma.
Hum Pathol. 2017; 65:225-230 [PubMed] Related Publications
CIC-rearranged sarcoma is a new entity of undifferentiated small round cell sarcoma characterized by chimeric fusions with CIC rearrangement. We report a NUTM2A-CIC fusion sarcoma in a 43-year-old woman who died of rapidly progressive disease. Histologic analysis revealed multinodular proliferation of small round tumor cells with mild nuclear pleomorphism. The sclerotic fibrous septa separated the tumor into multiple nodules. Immunohistochemistry showed that the tumor cells were diffusely positive for vimentin, focally positive for cytokeratin, and negative for CD99 and NKX2.2. Tumor cells were also negative for ETV4, which was recently identified as a specific marker for CIC-rearranged sarcoma. High-throughput RNA sequencing of a formalin-fixed, paraffin-embedded clinical sample unveiled a novel NUTM2A-CIC fusion between NUTM2A exon 7 and CIC exon 12, and fluorescence in situ hybridization identified CIC and NUTM2A split signals. This case shared several clinicopathological findings with previously reported CIC-rearranged cases. We recognized the tumor as a genetically distinct variant of CIC-rearranged sarcomas with a novel NUTM2A-CIC fusion.

Fusco N, Guerini-Rocco E, Augello C, et al.
Recurrent NAB2-STAT6 gene fusions and oestrogen receptor-α expression in pulmonary adenofibromas.
Histopathology. 2017; 70(6):906-917 [PubMed] Related Publications
AIMS: Pulmonary adenofibromas are rare benign fibroepithelial tumours of the lung with unknown histogenesis and an indolent clinical behaviour. Their stroma resembles that of solitary fibrous tumours, whereas the glands are composed of respiratory epithelium organized in a phyllodes-like architecture. Differentiation of pulmonary adenofibromas from other more aggressive intrathoracic tumours is clinically relevant. However, their biology is unknown. Here, we sought to characterize pulmonary adenofibromas at a clinicopathological level and to define whether they could be underpinned by a highly recurrent somatic genetic alteration akin to tumours with similar morphology.
METHODS AND RESULTS: Seven pulmonary adenofibromas were subjected to immunohistochemical analysis for thyroid transcription factor 1 (TTF1), napsin A, cytokeratin 7, E-cadherin, CD99, CD34, CD31, STAT6, oestrogen receptor (ER), progesterone receptor, androgen receptor, bcl-2, and vimentin, as well as electron microscopy and capillary sequencing on microdissected samples to evaluate the presence of NAB2-STAT6 fusion genes and MED12 exon 2 mutations in their discrete components. A control group comprising pulmonary solitary fibrous tumours, pulmonary hamartomas and breast fibroadenomas was also analysed. We confirmed that the stromal elements of pulmonary adenofibromas pertain to the fibroblastic lineage, and show ER overexpression in 71% of cases, whereas the epithelium consists of TTF1-positive, E-cadherin positive bronchiolar elements. A highly recurrent NAB2-STAT6 fusion variant (exon 4-exon 2) was detected in the stroma but not in the epithelium. No MED12 mutations were identified.
CONCLUSIONS: Here, we demonstrate that pulmonary adenofibromas are neoplastic lesions harbouring the molecular hallmark of solitary fibrous tumours.

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