Primary Renal Sarcoma With Gene Fusion in an 18-Year-Old Male: A Rare Lesion With a Diagnostic Quandary.

Primary renal sarcoma with gene fusion is a rare tumor with only 7 cases reported in the English literature. The morphologic features of this tumor strikingly overlap with clear cell sarcoma of the kidney and synovial sarcoma. Accurate diagnosis can be challenging. In this article, we report a case of an 18-year-old male who presented with hematuria. Subsequent imaging study showed a left renal mass with level II (infra-hepatic) inferior vena cava thrombus, which was resected. Detailed pathologic findings and immunohistochemical and molecular studies revealed an ovoid to spindle cell renal mass with a gene fusion.