Synovial Sarcoma With <i>BRAF</i> <scp>V600E</scp> Mutation: A Case Report and Literature Review

Synovial sarcoma (SS) is a genetically defined soft tissue sarcoma driven by the pathognomonic SS18::SSX fusion and is generally characterized by a low burden of secondary genomic alterations. We report a 42-year-old man with metastatic SS harboring both the SS18::SSX1 rearrangement and the BRAF V600E mutation. The patient developed metastatic disease following standard multimodal therapy. Comprehensive genomic profiling using DNA and RNA based next-generation sequencing identified the SS18::SSX1 fusion and the activating BRAF V600E mutation. The SS18 rearrangement was further confirmed by fluorescence in situ hybridization (FISH), and immunohistochemistry supported the histologic diagnosis. Treatment with combined BRAF and MEK inhibition (dabrafenib and trametinib) resulted in a clinical response. In addition to this index case, a literature review identified multiple additional SS harboring BRAF V600E, supporting its role as a recurrent, potentially targetable alteration in a small subset of SS. These findings highlight the value of comprehensive genomic profiling in SS, particularly in advanced or refractory cases, to identify rare but actionable molecular events that may expand therapeutic options.