Tip-147; CNS CIC-rearranged Sarcoma

Tip-147; CIC-rearranged sarcoma of the neural axis is a high-grade, poorly differentiated sarcoma defined by CIC gene fusion (19q13.2) with different gene partners. It occurs mostly in adolescents and young adults and presents primarily in the deep soft tissues with about 10% involving the viscera, including the CNS. Whether in the CNS or extra-cranial, CIC-rearranged sarcomas show similar histological features. The tumors are composed of sheets of highly undifferentiated small round cells interposed with foci of necrosis, a variably lobulated growth pattern, and desmoplastic stroma, that can show focal myxoid changes. There is predominance of round cells, but these can be intermixed with cells showing epithelioid and spindle cell morphology. Rhabdoid-like features including prominent nucleoli and eosinophilic cytoplasm can be seen also. By immunostains, the tumor cells are positive for CD99, and WT-1, but negative for NKX2.2. diagnosis needs to be confirmed by FISH studies or methylation profiling. These are aggressive tumors with dismal outcomes.