Gastric synovial sarcoma: the critical role of molecular techniques in diagnosis of an ultra-rare cancer.

Gastric synovial sarcoma (GSS) is an exceptionally rare mesenchymal malignancy, with only 51 cases reported. We present a case of a man in his 50s with dyspeptic symptoms and epigastric pain. Gastroscopy revealed an ulcerous tumour below the gastro-oesophageal junction. Histology, immunohistochemistry and molecular analysis confirmed SS18::SSX1 fusion, diagnostic of synovial sarcoma. The patient underwent successful robot-assisted partial gastric resection with negative margins. No recurrence was noted at 6-month follow-up. This case underscores the diagnostic challenge of GSS, the critical role of molecular techniques and the efficacy of minimally invasive surgical management.