Extraskeletal Ewing's sarcoma.

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Abstract

[Indexed for MEDLINE] 14. Jpn J Clin Oncol. 2025 Oct 7;55(10):1097-1104. doi: 10.1093/jjco/hyaf111. Update on the management of BCOR::CCNB3 sarcoma. Imanishi J(1), Sato K(1), Kikuchi Y(2), Yamamoto A(3), Watabe S(2), Matsuyama T(1), Sato C(3), Kobayashi H(4), Kawano H(1). Author information: (1)Department of Orthopaedic Surgery, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan. (2)Department of Pathology, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan. (3)Department of Radiology, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan. (4)Department of Orthopaedic Surgery, The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. BCOR::CCNB3 sarcoma is a rare sarcoma defined by the BCOR::CCNB3 fusion gene. It predominantly affects males under 20, with a slight predominance of bone origin. Initially grouped as 'Ewing-like,' it is now a distinct entity, a major part of 'sarcoma with BCOR genetic alterations.' Incidence is low, estimated at under 10 annual cases in Japan. Radiologically, it can mimic other high-grade sarcomas, with variable lytic or sclerotic bone lesions and nonspecific soft tissue findings. By contrast, it sometimes appears well-defined and benign-like. Pathologically, the detection of BCOR::CCNB3 fusion is key to diagnosis. Histology varies from small round cells to spindle cells, showing CD99, BCOR, Cyclin D1, and SATB2 positivity, with CCNB3 differentiating it from BCOR-ITD. Molecular testing confirms the diagnosis. Treatment involves wide resection and chemotherapy, with the Ewing sarcoma protocol often chosen. Approximately 20% are metastatic at diagnosis, and local recurrence after surgery occurs in as high as ⁓20% of BCOR::CCNB3 sarcomas. The relatively high local recurrence rate is probably because of the infiltrative growth. Complete response to neoadjuvant chemotherapy may indicate a better prognosis. Less frequent metastasis at diagnosis indicates that this sarcoma is less aggressive than Ewing sarcoma. Five-year overall survival is ⁓75%, but the prognosis of non-resectable or metastatic cases is worse. Further research is crucial for tailored treatment. Due to the tumor's super-rarity, collaborative, multi-institutional studies are essential, allowing for robust clinical trials and outcome analyses. Long-term follow-up studies are also necessary to assess late effects and survival. © The Author(s) 2025. Published by Oxford University Press. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com. DOI: 10.1093/jjco/hyaf111