Primary Renal Synovial Sarcoma Mimicking Transitional Cell Carcinoma: A Case Report

Primary renal synovial sarcoma (PRSS) is a rare malignant tumor with nonspecific imaging characteristics. This case concerns an 80-year-old man who presented with hematuria and flank pain. CT revealed a small left renal mass that rapidly enlarged over 3 months, with biopsy findings suggesting synovial sarcoma. A radical nephrectomy confirmed monophasic PRSS with SS18-SSX-positive staining. However, no recurrence was observed during the 2-year follow-up period. PRSS should be considered for atypical renal masses, and diagnosis requires histopathological examination combined with molecular testing.