BCOR-CCNB3 Sarcoma Research Articles

The diagnostic value of CCNB3 and BCOR expression in BCOR-CCNB3 sarcoma

Objective: To investigate the diagnostic value of expression of CCNB3 and BCOR in BCOR-CCNB3 sarcoma (BCS). Methods: Fifteen cases of BCS confirmed by fluorescence in situ hybridization (FISH) and/or reverse transcription-polymerase chain reaction (RT-PCR) from January 2014 to October 2021 at Beijing Jishuitan Hospital were collected. Immunohistochemical EnVision method was used to detect the expression of CCNB3 and BCOR in 15 cases of BCS and in 65 non-BCS tumors (54 cases of Ewing's sarcoma, 5 cases of CIC rearranged sarcoma, 4 cases of synovial sarcoma, 1 case of mesenchymal chondrosarcoma and 1 case of soft tissue clear cell sarcoma). Results: Immunohistochemical staining for CCNB3 revealed strongly diffuse nuclear staining in 14 of 15 (14/15) BCS cases, whereas none of the 65 non-BCS tumors showed any staining. Immunohistochemical staining for BCOR showed strongly diffuse nuclear staining in 11 (11/14) BCS cases; seven of the 65 (7/65, 10.8%) non-BCS tumors showed variable staining (five cases of Ewing sarcoma, one cases of synovial sarcoma, and one case of mesenchymal chondrosarcoma). The sensitivity and specificity of CCNB3 in diagnosing BCS were 93.3% and 100% and these of BCOR were 78.6% and 89.2%, respectively. Conclusions: CCNB3 is a highly sensitive and specific marker for BCS.The antibody may help screening BCS.

Prevalence of ultra-rare undifferentiated round cells sarcoma of bone and soft tissue after genomic classification.

11559 Background: Over the last decade, the category of undifferentiated round cell sarcomas (URCS), defined by the absence of Ewing sarcoma-associated translocations, has emerged. Aim of this study was to assess prevalence of each entity and outcome after genomic classification. Methods: Ewing sarcoma and other URCS diagnosed between 1920 and 2020 were reviewed. All URCS with available material were analyzed with FISH, RT-qPCR and/or Archer FusionPlex Sarcoma Panel. Demographic and treatment were collected. Survival was analyzed in patients with available follow-up. Results: 1995 cases identified, 20 cases lacked material for further genetic analysis and were excluded. 1975 cases were classified as follows: 1925 Ewing sarcomas (97.47%), 25 CIC-rearranged sarcomas (1.27%), 16 BCOR-CCNB3 rearranged sarcomas (0.81%), 2 EWSR1-NFATC2 sarcoma (0.1%), one each as CIC-LEUTX and FUS-NFATC2 rearranged sarcoma (0.05% each), and 5 as unclassified URCS (0.25%). A different presentation according to tumor type was shown in 43/50 ultra-rare tumors (Table). Forty-one/50 cases had available follow-up: 20/41 patients underwent surgery, 14/41 surgery+radiotherapy, 6 radiotherapy only, and no local treatment for 1 patient. Chemotherapy was administrated to 36/41 patients (Ewing sarcoma drugs in 16/22 CIC-DUX-4 and 8/11 BCOR-CCNB3; osteosarcoma drugs in 2/11 BCOR-CCNB3, and doxorubicin/ifosfamide in 2/22 CIC-DUX4 and 2/5 URCS; not specified in 6 cases). The 3-years overall survival (OS) was 32.7%f for CIC-rearranged sarcomas (75% in localize disease, 7,7% for the advanced disease, p 0.0084), 81.8% for BCOR-CCNB3 sarcomas (87.5% localized, 66.7% advanced; p 0.0734), and 60% for URCS (p 0.057). 1 patient with CIC-LEUTX sarcoma presenting with metastases died 13 months from diagnosis, 1 patient with FUS-NFATC2 and 1 with EWSR1-NFATC2 rearrenged sarcomas were alive without disease at 8 and 5 years from onset. Conclusions: Prevalence of URCS characterized by a combination of morphologic observation ad molecular techniques is provided. The majority of the cases underwent surgery or surgery combined with radiotherapy, and Ewing-like chemotherapy. The survival difference among different entities underscores the need of accurate subclassification of round cell sarcomas. Novel drugs for CIC-DUX-4 sarcomas presenting with metastases are needed. [Table: see text]

BCOR-CCNB3 sarcoma with concurrent RNF213-SLC26A11 gene fusion: a rare sarcoma with altered histopathological features after chemotherapy

BackgroundChemotherapy is a common approach for cancer treatment, but intrinsic genetic mutations in different individuals may cause different responses to chemotherapy, resulting in unique histopathological changes. The genetic mutation along with the distinct histopathological features may indicate new tumor entities. BCOR-CCNB3 sarcomas is a kind of Ewing-like sarcomas (ELS) occurring mostly in bone and soft tissues. No gene fusion other than BCOR-CCNB3 has been found in this type of tumor.Case presentationWe herein report a case of 17-year-old male patient, presented with a mass on his left shoulder that was diagnosed as undifferentiated small round cell sarcoma according to core biopsy. The patient received 5 courses of preoperational chemotherapy, and the tumor was resected and analyzed. Primitive small round cells and larger myoid cells in the resected tumor tissue but not in biopsy were observed, and arterioles stenosis and occlusion were also detected, indicating a dramatic change of histopathological features of this tumor. In addition, the immunohistochemical results showed the altered staining patterns of BCOR, bcl2, CyclinD1, TLE1, AR, SMA, CD117, STAB2, CD56, and CD99 in tumor tissues after chemotherapy. Notably, RNA sequencing revealed a RNF213-SLC26A11 fusion in the tumor sample.ConclusionsThe BCOR-CCNB3 sarcoma with RNF213-SLC26A11 fusion may indicate a subset of tumors that undergo histopathological changes in response to chemotherapy. More similar cases in the future may help to clarify the clinical meanings of RNF213-SLC26A11 fusion in BCOR-CCNB3 sarcomas and the underlying mechanisms.

Reassessment of EWSR1 gene rearrangement-negative undifferentiated round cell sarcomas in bone and soft tissues by fluorescence in situ hybridization

Objective: To unravel the CIC rearrangement sarcomas and BCOR-CCNB3 sarcomas from EWSR1 rearrangement-negative undifferentiated round cell sarcomas in the bone and soft tissues. Methods: Twenty-eight cases of EWSR1 rearrangement-negative undifferentiated round cell sarcomas of bone and soft tissues, tested for CIC rearrangement and BCOR rearrangement by fluorescence in situ hybridization and related immunostaining were analyzed, and some of the BCOR rearrangement cases were verified by reverse transcription-polymerase chain reaction. Results: Five of 28 (17.9%) tested cases were positive for CIC rearrangement and six (21.4%) for BCOR rearrangement. Histopathologically, CIC rearrangement sarcomas comprised nodular aggregates of round to polygonal cells, containing hyperchromatic nuclei, prominent nucleoli and moderate cytoplasm, with focal variable necrosis and myxoid stroma. BCOR-CCNB3 sarcomas mostly comprised diffusely arranged, round to oval to short spindly cells with angulated nuclei, vesicular chromatin, inconspicuous nucleoli and interspersed vessels. Immunohistochemically, five of six BCOR-CCNB3 sarcomas showed CCNB3 immunostaining, which could be helpful for diagnosis. Two patients with CIC rearrangement sarcoma died of the diseases in seven months and twenty-two months. One patient with BCOR-CCNB3 sarcoma died of the diseases in forty-six months. Conclusions: Overall, 39.3% of the EWSR1 rearrangement-negative undifferentiated round cell sarcomas are CIC rearrangement sarcomas and BCOR-CCNB3 sarcomas. Molecular testing is helpful for diagnosis.

Imaging features and clinical course of undifferentiated round cell sarcomas with CIC-DUX4 and BCOR-CCNB3 translocations.

To describe the pre-treatment imaging features and clinical course of undifferentiated round cell sarcomas with CIC-DUX4 and BCOR-CCNB3 translocations. In this retrospective study, several pre-treatment imaging features (tumor location, size, enhancement pattern, necrosis, flow voids, calcification, and FDG avidity) and the clinical course of patients were evaluated. In 12 patients with CIC-DUX4 sarcomas (median age, 24 years; range, 12-75), sarcomas were located in the soft tissue (n = 10), bone (n = 1), and lungs (n = 1). On MRI, all 10 CIC-DUX4 sarcomas presented as a large necrotic mass (mean size 6.7 cm, range 2.3-11.3) with 100% demonstrating contrast enhancement, 60% showing flow voids, and 20% demonstrating fluid-fluid levels. On PET, the mean SUVmax was 13.2 (range, 8.5-18.1). Among 12 patients with follow-up, 3 died within a year of diagnosis. The most common site of metastases was the lungs (5/12). In 5 patients with BCOR-CCNB3 sarcomas (median age, 14 years; range, 2-17), sarcomas were located in the spine (n = 2), femur (n = 1), tibia (n = 1), and pelvis (n = 1). On radiograph or CT, 2 were lytic, 3 were sclerotic. Soft tissue calcifications occurred in 40% of BCOR-CCNB3 sarcomas. On MRI, all 3 BCOR-CCNB3 tumors enhanced with 33% demonstrating flow voids and 66% exhibiting necrosis. On PET, the mean SUVmax was 6.3 (range 5.7-6.9). CIC-DUX4 sarcomas often present as necrotic and hypermetabolic soft tissue masses while sarcomas with BCOR-CCNB3 translocations are vascular bone lesions with necrosis at imaging. CIC-DUX4 sarcomas are clinically more aggressive than BCOR-CCNB3 sarcomas.

Abstract 3411: High-throughput drug screening combined with a druggable target CRISPR drop-out screen identifies therapeutic vulnerabilities of BCOR-CCNB3 fusion positive sarcomas

Abstract Undifferentiated round cell sarcomas, which carry the BCOR-CCNB3 fusion gene, have traditionally been called “Ewing-like sarcomas” and have been treated with Ewing sarcoma treatment regimens. While there has been emerging evidence that these BCOR-CCNB3 sarcomas (BCS) are molecularly distinct from Ewing sarcomas, the biology of these tumors is poorly understood, and patients have few options when they do not respond to Ewing sarcoma-based therapies. Here, we report the establishment of a novel BCS cell line, which we utilized to identify a unique BCS-specific therapeutic vulnerability using a hybrid screening approach consisting of a high-throughput drug screen combined with a CRISPR/Cas9-based knock out genetic screen. The BCOR-CCNB3-positive sarcoma cell line NBC-1 was established from the tumor tissue obtained from an 18-year-old male with a soft tissue tumor of the buttock with lymph node metastasis, and the expression of the fusion BCOR-CCNB3 transcript was confirmed by RT-PCR. An in vitro high-throughput screening was performed using the L1300 library of 2570 drugs, where the cells were incubated for 48 hours with drug before cell viability was measured. This drug screen identified 148 drugs, which included 84 FDA-approved drugs. While these drugs predictably included a significant number of conventional cytotoxic chemotherapy drugs currently used to treat BCS, such as vincristine and doxorubicin, several other drug classes emerged, identifying twenty tyrosine kinase inhibitors, proteasome inhibitors such as Carfizomib, Ixazomib, and Bortezomib, and a histone deacetylase inhibitor, Panobinostat, all of which had distinctly higher cytotoxicity compared to the Ewing sarcoma cell controls. Next, we utilized a custom-made CRISPR panel consisting of 9771 sgRNAs targeting 1221 genes where we were able to identify a specific pharmacologic inhibitor in the literature. Using this library, we carried out a genetic loss-of-function screen to identify genes that are required for the proliferation of BCS. Based on these initial findings, we were able to demonstrate that BCS tumors have distinct vulnerabilities from Ewing sarcoma, suggesting that a BCS-specific therapeutic approach is necessary. Citation Format: Naoki Oike, Hiroyuki Kawashima, Akira Ogose, Takashi Ariizumi, Yudai Murayama, Hajime Umezu, Molishree Joshi, Colin Sempeck, Deandra Warker, Avery Bodlak, Naoto Endo, Masanori Hayashi. High-throughput drug screening combined with a druggable target CRISPR drop-out screen identifies therapeutic vulnerabilities of BCOR-CCNB3 fusion positive sarcomas [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3411.

From This Month's Histopathology

From This Month's Histopathology

Expanding the clinicopathologic and molecular spectrum of BCOR-associated sarcomas in adults.

BCOR gene alteration is a genetic signature of rare subsets of sarcomas. Most BCOR-associated sarcomas thus far reported are in the pediatric population, except for uterine sarcomas. We studied seven cases of BCOR-associated non-uterine sarcomas in adult patients. The patients were four men and three women ranging from 26 to 71years in age. Three tumors, two of which primarily affected the kidney, showed BCOR-CCNB3. One tumor with a ZC3H7B-BCOR occurred in the chest wall, and a tumor with a novel CIITA-BCOR was found in the sinonasal tract. Two tumors in the lung and breast harbored exon 15 internal tandem duplications of BCOR, a highly unexpected observation in this age group. All seven sarcomas consisted of dense proliferations of uniform round to spindle cells with fine chromatin within vascular stroma. BCOR-CCNB3 sarcomas showed swirling fascicular growth. The tumor with the ZC3H7B-BCOR fusion showed a multinodular growth of spindle cells, and the tumors with the CIITA-BCOR fusion showed palisading of oval cells. Both tumors with BCOR internal tandem duplication demonstrated nested to palisading growth of round cells within sclerotic non-myxoid stroma. All seven sarcomas diffusely expressed BCOR and SATB2 immunohistochemically, with all three BCOR-CCNB3 sarcomas being immunopositive for CCNB3. BCOR alterations were confirmed by RNA sequencing, polymerase chain reaction, Sanger sequencing, and/or fluorescence in situ hybridization. This study expands the clinicopathologic and molecular spectrum of BCOR-associated sarcomas, and emphasizes the importance of being aware of this entity in the differential diagnosis of adult non-uterine sarcomas.

NTRK3 overexpression in undifferentiated sarcomas with YWHAE and BCOR genetic alterations.

The BCOR family of tumors includes a number of undifferentiated sarcomas, occurring in various age groups and anatomic sites, characterized by a spindle and round cell phenotype and diffuse immunoreactivity for BCOR. Prior RNA sequencing data revealed that NTRK3 was a top upregulated gene in BCOR-CCNB3 sarcomas. In this study we investigate a large cohort of tumors harboring BCOR/YWHAE genetic alterations for NTRK3 upregulation at both the mRNA and protein levels, compared to other sarcoma types. Pan-Trk immunohistochemistry was assessed for intensity and extent. A correlation between NTRK3 expression and the type of BCOR alteration and BCOR immunoreactivity was also performed. Most soft tissue undifferentiated round cell sarcomas with YWHAE or BCOR rearrangements or BCOR internal tandem duplications (ITD) showed NTRK3, but not NTRK1 or NTRK2, up-regulation by RNA sequencing data analysis. Cytoplasmic pan-Trk immunoreactivity was also observed in most soft tissue round cell sarcomas with YWHAE rearrangements (100%), BCOR ITD (80%), and BCOR-CCNB3 fusions (67%), as well as clear cell sarcomas of kidney (75%), another BCOR family tumor, and ossifying fibromyxoid tumors with ZC3H7B-BCOR fusion (100%), with variable staining intensity and extent. Pan-Trk staining was also seen in solitary fibrous tumors (100%) and less frequently in synovial sarcoma and Ewing sarcoma, but rarely in other sarcomas tested. Tumors harboring rare fusion variants of BCOR, such as BCOR-CHD9, a novel fusion identified by targeted RNA sequencing, and KMT2D-BCOR, were also positive for pan-Trk staining and NTRK3 overexpression. In conclusion, NTRK3 upregulation resulting in pan-Trk overexpression is common in the BCOR family of tumors as well as in subsets of BCOR expressing sarcomas through alternative mechanisms. The therapeutic implication of this finding awaits further investigation.

PAX7 immunohistochemical evaluation of Ewing sarcoma and other small round cell tumours.

Ewing sarcoma is a small round cell tumour that affects bone and soft tissues. Although the detection of the specific fusion gene is a robust method of its diagnosis, immunohistochemistry may serve as a practical surrogate. Recent tissue microarray studies suggested that PAX7 is a novel marker, because it was expressed consistently in Ewing sarcoma, in addition to rhabdomyosarcoma and synovial sarcoma. Here, we evaluated the utility of PAX7 immunohistochemistry in whole-tissue sections of an expanded array of round cell malignancies with adequate molecular characterisation. We stained 30 molecularly confirmed Ewing sarcomas, one EWSR1-NFATC2 sarcoma and 141 non-Ewing round cell tumours by a monoclonal antibody against PAX7. Staining was considered positive if at least 5% of tumour cells were stained. PAX7 was expressed in 27 of 30 Ewing sarcomas (90%), mainly in a diffuse and strong manner. Although NKX2-2 showed similar sensitivity, PAX7 showed more extensive and strong reactivity. One EWSR1-NFATC2 sarcoma co-expressed PAX7 and NKX2-2. PAX7 was also expressed in 24 of 141 non-Ewing tumours, including alveolar rhabdomyosarcomas (seven of 10), poorly differentiated synovial sarcomas (seven of 10), BCOR-CCNB3 sarcomas (eight of 10), small-cell osteosarcoma (one of five) and desmoplastic small round cell tumour (one of 10), one-third of which showed diffuse strong reactivity. Although we confirmed that PAX7 is a sensitive marker for Ewing sarcoma, anti-PAX7 antibody also stained several Ewing sarcoma mimics, whose spectrum was distinct from NKX2-2-positive non-Ewing entities. Further studies are required to determine how PAX7 could be integrated into practice to classify small round cell tumours efficiently.

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.

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.

Clear cell sarcomas of the kidney are characterised by BCOR gene abnormalities, including exon 15 internal tandem duplications and BCOR-CCNB3 gene fusion.

Clear cell sarcoma of the kidney (CCSK) is a rare paediatric renal malignant tumour. The majority of CCSKs have internal tandem duplications (ITDs) of the BCOR gene, whereas a minority have the YWHAE-NUTM2 gene fusion. A third 'double-negative' (DN) category comprises CCSKs with neither BCOR ITDs nor YWHAE-NUTM2 fusion. The aim of this study was to characterise 11 histologically diagnosed CCSKs immunohistochemically (with CCND1, BCOR and CCNB3 stains) and genetically. By next-generation sequencing, 10 cases (90.9%) had BCOR exon 15 ITDs, with positive BCOR immunoreactivity being found in four (36%) or eight (72%) cases, depending on the antibody clone. By reverse transcription polymerase chain reaction, none had the YWHAE-NUTM2 fusion. The DN case had a BCOR-CCNB3 fusion and strong nuclear CCNB3 and BCOR immunoreactivity. Quantitative polymerase chain reaction showed markedly elevated BCOR expression in this case, whereas BCOR ITD cases had lower levels of elevated BCOR expression. The majority of the CCSKs in our cohort had BCOR ITDs, and none had the YWHAE-NUTM2 fusion. We verified the strong, diffuse cyclin D1 (CCND1) immunoreactivity in CCSKs described in recent reports. BCOR immunoreactivity was not consistently positive in all CCSKs with BCOR ITDs, and therefore cannot be used as a diagnostic immunohistochemical stain to identify BCOR ITD cases. The DN case was a BCOR-CCNB3 fusion sarcoma. BCOR-CCNB3 sarcoma is typically a primary bone sarcoma affecting male adolescents, and this is the first report of it presenting in a kidney of a young child as a CCSK. The full spectrum of DN CCSKs awaits more comprehensive characterisation.

SATB2 and TLE1 Expression in BCOR-CCNB3 (Ewing-like) Sarcoma, Mimicking Small Cell Osteosarcoma and Poorly Differentiated Synovial Sarcoma

SATB2 and TLE1 Expression in BCOR-CCNB3 (Ewing-like) Sarcoma, Mimicking Small Cell Osteosarcoma and Poorly Differentiated Synovial Sarcoma

Histological and immunohistochemical characteristics of undifferentiated small round cell sarcomas associated with CIC-DUX4 and BCOR-CCNB3 fusion genes.

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.

ETV4 is a useful marker for the diagnosis of CIC-rearranged undifferentiated round-cell sarcomas: a study of 127 cases including mimicking lesions

Subsets of primitive round-cell sarcomas remain difficult to diagnose and classify. Among these is a rare round-cell sarcoma that harbors a CIC gene rearrangement known as CIC-rearranged undifferentiated round-cell sarcoma, which is most commonly fused to the DUX4 gene. Owing to its aggressive clinical behavior and potential therapeutic implications, accurate identification of this novel soft tissue sarcoma is necessary. Definitive diagnosis requires molecular confirmation, but only a few centers are as yet able to perform this test. Several studies have shown that PEA3 subfamily genes, notably ETV4 (belonging to the family of ETS transcription factors), are upregulated in CIC-rearranged undifferentiated round-cell sarcomas. We performed a detailed immunohistochemical analysis to investigate ETV4 expression in CIC-rearranged undifferentiated round-cell sarcomas and their potential mimics (especially Ewing sarcomas). The study cohort included 17 cases of CIC-rearranged undifferentiated round-cell sarcomas, and 110 tumors that morphologically mimic CIC-rearranged undifferentiated round-cell sarcomas: 43 Ewing sarcomas, 25 alveolar rhabdomyosarcomas, 20 poorly differentiated round-cell synovial sarcomas, 10 desmoplastic round-cell tumors, 5 BCOR-CCNB3 sarcomas, 5 lymphoblastic lymphomas, and 2 rhabdoid tumors. All CIC-rearranged undifferentiated round-cell sarcomas (on core needle biopsies and open biopsies) were ETV4-positive with a strong diffuse nuclear pattern. Among the other 110 tumors, only six cases (four Ewing sarcomas, one alveolar rhabdomyosarcoma, and one desmoplastic round-cell tumor) showed focal (<5% of tumor cells) and very weak nuclear expression of ETV4; all other tumors were completely negative for ETV4. We conclude that systematic immunohistochemical analysis of ETV4 makes it possible to diagnose undifferentiated round-cell sarcomas (with no molecular markers for sarcoma-associated translocation) such as CIC-rearranged undifferentiated round-cell sarcoma.

503O_PR CIC-rearranged sarcoma and BCOR-CCNB3 sarcoma: Clinical characteristics and treatment results of the newly-established “Ewing sarcoma-like” small round cell sarcomas

503O_PR CIC-rearranged sarcoma and BCOR-CCNB3 sarcoma: Clinical characteristics and treatment results of the newly-established “Ewing sarcoma-like” small round cell sarcomas

503O_PR CIC-rearranged sarcoma and BCOR-CCNB3 sarcoma: Clinical characteristics and treatment results of the newly-established “Ewing sarcoma-like” small round cell sarcomas

503O_PR CIC-rearranged sarcoma and BCOR-CCNB3 sarcoma: Clinical characteristics and treatment results of the newly-established “Ewing sarcoma-like” small round cell sarcomas

Evaluation of ETV4 and WT1 expression in CIC-rearranged sarcomas and histologic mimics

AbstractA distinct subset of round cell sarcomas harbors capicua transcriptional repressor (CIC) rearrangement. Diagnosing these sarcomas can be difficult owing to their resemblance to Ewing sarcoma and other 'small round blue cell tumors'; molecular techniques are generally required. Recent gene expression studies of CIC-rearranged sarcomas identified the upregulation of ETV4. We assessed the sensitivity and specificity of ETV4 and WT1 immunohistochemistry for CIC-rearranged sarcoma. We evaluated whole-tissue sections from 40 CIC-rearranged sarcomas, 40 Ewing sarcomas, 4 BCOR-CCNB3 sarcomas, 6 unclassified round cell sarcomas, and 150 histologic mimics. Moderate-to-strong nuclear immunoreactivity for ETV4 in at least 50% of cells was observed in 36 (90%) CIC-rearranged sarcomas and 10 (5%) other tumors, including 5 unclassified round cell sarcomas, 2 Wilms tumors, and 1 each desmoplastic small round cell tumor, melanoma, and small cell carcinoma. Thirty-eight (95%) CIC-rearranged sarcomas showed nuclear staining for WT1, and 34 (85%) were positive for both ETV4 and WT1. Of 182 other tumors evaluated, 34 (19%) showed nuclear WT1 positivity, including all Wilms tumors and desmoplastic small round cell tumors, 5 unclassified round cell sarcomas, and a subset of lymphoblastic lymphomas, rhabdomyosarcomas, mesenchymal chondrosarcomas, carcinomas, and melanomas. In summary, diffuse moderate-to-strong ETV4 expression is present in most CIC-rearranged sarcomas and unclassified round cell sarcomas. More limited expression is seen in small subsets of various other round cell neoplasms. Nuclear WT1 expression is also present in most CIC-rearranged sarcomas and unclassified round cell sarcomas, along with Wilms tumors and desmoplastic small round cell tumors, and subsets of various histologic mimics. The sensitivity and specificity of diffuse ETV4 expression for CIC-rearranged sarcomas are 90% and 95%, respectively, whereas the sensitivity and specificity of WT1 are 95% and 81%, respectively. Diffuse ETV4 along with at least focal WT1 expression is helpful to distinguish CIC-rearranged sarcoma from Ewing sarcoma and other histologic mimics.

UNDIFFERENTIATED ROUND CELL SARCOMA WITH BCOR-CCNB3 TRANSLOCATION IN THE JAW OF A CHILD

To present a pediatric case of a rare BCOR-CCNB3 sarcoma of the mandible that phenotypically mimics Ewing sarcoma and to review the clinical, pathologic, molecular, and therapeutic features of this tumor.

BCOR-CCNB3-positive soft tissue sarcoma with round-cell and spindle-cell histology: a series of four cases highlighting the pitfall of mimicking poorly differentiated synovial sarcoma.

BCOR-CCNB3 sarcoma is a genetically defined undifferentiated malignancy with Ewing sarcoma (ES)-like round cells, and preferentially affects the bones of male adolescents. Sarcomas harbouring BCOR-CCNB3 rarely arise from soft tissues; therefore, we aimed to report four cases to expand the clinicopathological spectrum. By reverse transcription polymerase chain reaction and confirmatory sequencing, we detected a BCOR-CCNB3 transcript in primary undifferentiated sarcomas of the deep musculature of four male patients, comprising two teenagers (aged 14 and 17 years) and two adults (aged 34 and 44 years). The tumours originated in the back (n = 2), pelvis (n = 1), and thigh (n = 1), and were 70-140 mm in size (mean, 107 mm). All tumours showed sheets of primitive round or ovoid cells with vesicular nuclei, active mitosis (28-41/10 high-power fields), variably prominent nucleoli, and geographical necrosis. This major component transformed into fascicles of elongated spindle cells with staghorn vessels and a myxoid reticular stroma, accounting for 10-50% of areas. All cases were positive for CD99, three were positive for TLE1, and one was positive for EMA, indicating poorly differentiated synovial sarcomas (PDSSs). Nuclear cyclin B3 reactivity was present in all cases, but not in molecularly confirmed atypical ESs and PDSSs. At the last follow-up (median, 13.5 months), one patient had died of lung metastasis, two were alive with tumours, and one was tumour-free. BCOR-CCNB3-positive sarcomas may primarily occur in soft tissues of adults and show PDSS-mimicking round-cell and spindle-cell histology with aggressive behaviour. Cyclin B3 is useful for selecting candidates for BCOR-CCNB3 molecular testing.