A case of CIC‐rearranged sarcoma with CIC‐LEUTX gene fusion in spinal cord

A 16‐year‐old male was admitted to the hospital for weakness of both lower extremities. Magnetic resonance imaging revealed an intraspinal extramedullary subdural mass at the thoracic 9 level. Microscopically, the tumor cells were small to medium sized and round to ovoid in shape. They were distributed in diffuse sheets or showed nodular appearance. The nucleus of the tumor had mild‐to‐moderate atypia, with vesicular chromatin and prominent nucleoli. A smaller proportion of tumor cells demonstrated rhabdoid morphology. Focal myxoid stromal change was present, in which tumor cells exhibited spindle shapes. Approximately two mitoses were counted per 10 high‐power fields. No necrosis was observed. The tumor cells were focal positive for CD99; multifocal positive for WT1; diffuse positive for nestin, synaptophysin, and D2‐40; partial positive for GFAP; focal positive for desmin and SSTR2; and scattered positive for S‐100 protein. The Ki‐67 labeling index was approximately 20%. Genetic testing revealed CIC‐LEUTX gene fusion. Considering the patient's history, clinical data, pathological findings and genetic findings, we rendered a rare tumor named CIC‐rearranged sarcoma with CIC‐LEUTX gene fusion.