Abstract
BACKGROUND: Synovial sarcoma is an uncommon soft tissue malignancy that mainly occurs near tendon sheath and bone joints. Primary intra-abdominal location is exceedingly rare and characterized by non-specific clinical signs. CASE PRESENTATION: We report the case of a young female without medical history who presented with acute abdominopelvic pain. Ultrasound echography revealed a right mass measuring 7 cm in greater diameter cystic with solid areas, likely of ovarian origin. A coelioscopy with peritoneal biopsies was performed. Histological examination with immunohistochemistry concluded the diagnosis of GIST. The patient was referred to the surgery department and after laboratory routine analysis and computed tomography, the patient was proposed to surgical management. Per-operative findings revealed a mesenteric mass locally invading the greater omentum and the appendicular wall. Pathological examination with immunochemistry confirmed the diagnosis of mesenteric monophasic synovial sarcoma invading the appendicular wall with positive surgical margins. Chemotherapy was proposed with a good response. Our patient is free from disease 9 months later. CONCLUSIONS: We aimed through this case report to discuss mesenteric presentation monophasic SS, mimicking ovarian malignancy, emphasizing clinicopathological features and differential diagnoses.