Objective: To investigate the histopathologic, immunohistochemical, molecular genetic characteristics of CIC-rearranged sarcoma (CRS) with rhabdoid features. Methods: The clinical and pathologic data of two cases of CRS diagnosed between 2019 and 2021 at the Department of Pathology, Jiangsu Province Hospital were analyzed. Immunohistochemical study and fluorescence in situ hybridization (FISH) were performed. The relevant literature was reviewed. Results: Both patients were female, one was 58 years old, with tumor located in left thigh; the other was 43 years old, with tumor located in left pelvic cavity. Microscopically, both tumors were composed of small to medium-sized round, oval cells, arranged in nodules or sheets. The tumor cells showed irregular nuclear outline, coarse chromatin with prominent nucleoli and brisk mitotic activity. Both cases showed rhabdoid phenotype with myxoid stromal changes. Immunohistochemically, both cases were positive for CD99 and c-myc. High WT1 reactivity was seen in classic area, with low reactivity in rhabdoid area. There was no INI1 lost in both cases. Both were negative for NKX2.2 and NKX3.1. By FISH both cases demonstrated convincing break-apart signals of CIC gene. One patient died of disease after 1 month, and the other died of disease after 3 months. Conclusions: CRS is a small round cell undifferentiated sarcoma of the bone and soft tissue defined by molecular genetic characteristics, and may show atypical morphologic and immunophenotypic characteristics such as rhabdoid features. A correct understanding of its rare morphologic and immunophenotypic characteristics, combined with molecular pathologic detection, is conducive to correct diagnosis.
目的： 探讨伴横纹肌样特征CIC重排肉瘤（CIC-rearranged sarcoma，CRS）的组织形态学、免疫组织化学及分子遗传学特征。 方法： 回顾性分析2019—2021年江苏省人民医院（南京医科大学第一附属医院）病理学部诊断的2例伴横纹肌样特征CRS临床病理学资料，行免疫组织化学及荧光原位杂交检测，并复习相关文献。 结果： 2例患者均为女性，年龄分别为58岁和43岁，肿瘤分别位于左大腿及左盆腔。肿瘤结节状或实性片状分布，小至中等大小的圆形、卵圆形细胞组成，核形不规则，常可见核仁，核分裂象易见，肿瘤间质黏液样变性，可见横纹肌样肿瘤细胞。免疫表型：2例肿瘤CD99、c-myc均阳性；肿瘤WT1经典区高表达，横纹肌样特征区低表达；但INI1均未缺失；NKX2.2、NKX3.1均阴性。采用断裂分离探针荧光原位杂交检测显示2例均CIC基因重排。2例患者分别于诊断后1个月及3个月死亡。 结论： CRS是一种由分子遗传学特征定义的骨及软组织小圆细胞未分化肉瘤，可能出现横纹肌样特征等不典型的形态学和免疫表型，正确认知其罕见的形态学、免疫表型特征，辅以分子病理检测，有助于正确诊断。.