Primary Spindle Cell Sarcoma of the Lung with MGA::NUTM1 Fusion: An Extremely Rare Case of a Potentially Emerging Entity and Review of the Literature.

Originally described in a rare subset of poorly differentiated squamous cell carcinomas termed NUT carcinomas, NUTM1 rearrangements are now known to characterize a wide spectrum of neoplasms including sarcomas, poromas/porocarcinomas, unclassified adnexal carcinomas and pediatric acute lymphoblastic leukemia. The advent of next-generation sequencing (NGS) has led to the identification of a multitude of novel fusion partners in addition to BRD4 , which was initially reported in the majority of NUT carcinomas. NUTM1 -rearranged sarcomas usually harbor fusions with the MAD gene family ( MXD1 , MXD4 , MGA ) and present as spindle cell proliferations in diverse locations in patients of all ages. Herein, we present a very rare case of spindle cell sarcoma of the lung, which harbored a NUTM1::MGA fusion and offer a comprehensive update of the recent data.