摘要目的:筛选EWSR1基因重排阴性的未分化小圆细胞肉瘤中的CIC重排肉瘤（CRS）或BCOR-CCNB3肉瘤（BCS），总结其临床病理特征。方法:收集北京积水潭医院病理科2014年1月至2020年9月病理诊断为未分化小圆细胞肉瘤且疑为尤文肉瘤但荧光原位杂交（FISH）未检测到EWSR1基因重排的病例28例，采用FISH检测CIC基因断裂及BCOR基因断裂情况，从中筛选出CRS或BCS，部分BCS经逆转录聚合酶链反应（RT-PCR）验证。结果:筛选出CRS 5例，BCS 6例，各占EWSR1基因重排阴性的未分化小圆细胞肉瘤的17.9%（5/28）和21.4%（6/28），两者总占比为39.3%（11/28）。CRS 5例中男性4例，女性1例，年龄15~65岁。其中4例发生于软组织，1例发生于骨组织。肿瘤细胞稍大，泡状核，核仁明显，呈弥漫片状、分叶状或血管周生长，间质可见纤维间隔，部分黏液变。肿瘤细胞不同程度表达CD99，部分病例表达Fli-1、TLE1、DUX4、WT-1、Calretinin。5例CRS患者随访7~22个月，2例死亡，2例无瘤生存，1例失访。BCS 6例中男性5例，女性1例，年龄8~20岁。其中4例发生于骨组织，2例发生于软组织。肿瘤细胞短梭形或卵圆形，核染色质细腻，核仁不明显，排列成实性或束状生长，间质富于毛细血管网，间或有细胞稀疏区伴间质黏液变。肿瘤细胞表达TLE1、CCNB3，少部分病例表达CD99、Fli-1。3例经RT-PCR验证为BCOR-CCNB3基因融合。6例BCS患者随访1~68个月，1例死亡，5例无瘤生存。结论:39.3%的EWSR1基因重排阴性的未分化小圆细胞肉瘤为CRS或BCS肉瘤，分子检测有助于其正确诊断。

abstractsObjective: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.