Abstract Synovial sarcoma is uncommonly documented in the pelvis. Rarely, such cases have dealt with molecular analysis. A 32-year-old boy presented with pain and swelling in his left lower limb of two three duration. He developed acute urinary retention four days prior to his hospital admission, wherein radiological examination unraveled a large soft tissue mass displacing his pelvic muscles, along with a lesion involving his left public bone. Biopsy showed a cellular spindle cell sarcoma, exhibiting hemangiopericytoma-like vascular patter with focal necrosis. Diagnosis of a differentiated synovial sarcoma was offered and confirmed.