NUTM2A-CIC fusion small round cell sarcoma: A genetically distinct variant of CIC-rearranged sarcoma

Publication date: Available online 8 February 2017
Source:Human Pathology
Author(s): Shintaro Sugita, Yasuhito Arai, Tomoyuki Aoyama, Hiroko Asanuma, Wakako Mukai, Natsuko Hama, Makoto Emori, Tatsuhiro Shibata, Tadashi Hasegawa
CIC-rearranged sarcoma is a new entity of undifferentiated small round cell sarcoma characterized by chimeric fusions with CIC-rearrangement. We report a NUTM2A-CIC fusion sarcoma in a 43-year-old woman who died of rapidly progressive disease. Histologic analysis revealed multinodular proliferation of small round tumor cells with mild nuclear pleomorphism. The sclerotic fibrous septa separated the tumor into multiple nodules. Immunohistochemistry showed that the tumor cells were diffusely positive for vimentin, focally positive for cytokeratin, and negative for CD99 and NKX2.2. Tumor cells were also negative for ETV4, which was recently identified as a specific marker for CIC-rearranged sarcoma. High throughput RNA sequencing of a formalin-fixed paraffin embedded clinical sample unveiled a novel NUTM2A-CIC fusion between NUTM2A-exon 7 and CIC-exon 12, and fluorescence in situ hybridization identified CIC and NUTM2A split signals. This case shared several clinicopathological findings with previously reported CIC-rearranged cases. We recognized the tumor as a genetically distinct variant of CIC-rearranged sarcomas with a novel NUTM2A-CIC fusion.



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