[Clinicopathologic analysis of Ewing-like BCOR-CCNB3 undifferentiated sarcoma].

Objective: To investigate the morphologic, immunohistochemical, genetic, clinical features and prognosis of Ewing-like BCOR-CCNB3 gene fusion undifferentiated sarcoma (BCOR-CCNB3 fusion sarcoma). Method: Seventeen Ewing-like sarcoma cases were screened for CCNB3 expression and BCOR-CCNB3 fusion transcripts by immunohistochemistry and RT-PCR among 260 cases of Ewing-like sarcomas collected during Jan, 2006 to Dec, 2015. Three cases of BCOR-CCNB3 fusion sarcoma were found among 17 atypical Ewing sarcomas, and follow-up were conducted. Results: The harboring of BCOR-CCNB3 fusion transcript was confirmed by RT-PCR and directly sequencing results. The three patients aged between 8 and 11 years old. Two of them were male and the other one was female. One patient achieved a complete response after chemotherapy, the other two died without chemotherapy after surgical excision in 12 months. Tumor cells in all 3 cases showed diffuse nuclear CCNB3, TLE1 and cyclin D1 positivity, while CCNB3 (0/12), TLE1 (1/12) and cyclin D1 (4/12) positivity was infrequent in the 12 cases of classical Ewing's sarcoma. The oval or plump spindle tumor cells with fine chromatin arranged in solid pattern, the nucleoli was inconspicuous. The delicate capillary networks were obvious in the tumor. Conclusion: With a detailed description of the histological spectrum, immunohistochemical features and clinical characteristic of BCOR-CCNB3 sarcoma, justify distinction from Ewing sarcoma could be possible.