A rare case report of omental synovial sarcoma complicated hemoperitoneum and literature review.

Background: Synovial sarcoma is a rare malignant soft tissue tumor originating mainly in the extremities and usually related to the joint capsule, tendon sheath, or synovial capsule. Only a few cases of synovial sarcoma arising in the abdomen, particularly the omentum, have been reported. We presented a case of omental synovial sarcoma and reviewed 7 cases of this disease.

Case Presentation: A 37-year-old man presented to the hospital with abdominal pain and distension for 2 months. A computed tomography scan revealed a massive heterogeneous low attenuation mass with amorphous solid components between the stomach and colon with suspected hemoperitoneum. The patient underwent surgery, and the pathological result demonstrated a greater omentum biphasic synovial sarcoma. Chemotherapy was administered with a good response. He has no signs of recurrence during 3 years of follow-up. Among 7 cases of omental synovial sarcoma, the mean age was 42, ranging from 16 to 66 years old with predominantly female (71.4%), tumor size from 9.5 cm to 20 cm. Biphasic synovial sarcoma accounted for 50%. The recurrence rate within one year is high (57.1%).

Conclusions: Primary omental synovial sarcoma is uncommon and presents with nonspecific clinical symptoms, often leading to potential misdiagnosis with other conditions before surgery. They occur predominantly in females, mainly middle-aged, with a large mass size before presentation. Due to the high recurrence and mortality rate, it needs to be recognized at the early stage.