Abstract
Synovial sarcoma (SS) is an uncommon malignant tumor, ranking third in prevalence within the soft tissue sarcomas group. The vast majority of synovial sarcomas are present in the extremities, with only 15% developing in the retroperitoneal space. Retroperitoneal synovial sarcoma (RSS) is an infrequent case of SS, with only about 20 cases reported in the literature. Diagnosing RSS before treatment remains challenging because of its nonspecific clinical symptoms. The disease is often detected at a later stage, leading to additional damage to other organs as well as complicated and ineffective treatment. Consequently, the 5-year survival rate is only 20%-29%. This report introduces a case of RSS in a 19-year-old male patient with imaging characteristics on computed tomography (CT) and magnetic resonance (MR).