Pelvic Synovial Sarcoma Clinically Masquerading as an Ovarian Malignancy

Background: Synovial sarcoma, a malignant mesenchymal tumor, commonly involves the extremities and is rarely found in the pelvis. Cytology with a biphasic pattern can suggest the diagnosis of synovial sarcoma. Case Report: A 32-year-old female presented with complaints of abdominal distension. She was initially evaluated in another hospital where she underwent ultrasound-guided fine needle aspiration cytology (FNAC) of the abdominal mass. The mass was diagnosed as ovarian adenocarcinoma, and the patient underwent 3 cycles of chemotherapy. After 3 months, she was referred to our institute for surgical excision of the mass. Contrast-enhanced computed tomography of the abdomen suggested a well-circumscribed, heterogeneous, solid-cystic mass in the left adnexal region measuring 13.9 × 10 × 9.1 cm and compressing the adjacent structures. No previous radiologic investigations were available. We reviewed the FNAC slide from the outside hospital and made a preliminary diagnosis of biphasic synovial sarcoma. The patient underwent debulking surgery consisting of panhysterectomy with excision of the pelvic mass. Microscopic examination of the pelvic mass showed a biphasic tumor composed of epithelial and mesenchymal components, suggestive of synovial sarcoma. The immunohistochemistry profile supported the morphologic diagnosis. Bilateral ovaries were unremarkable. The patient received 4 cycles of adjuvant chemotherapy and is presently asymptomatic. Conclusion: Although primary pelvic synovial sarcoma is a rare occurrence, this case illustrates that synovial sarcoma can be diagnosed or at least suspected on FNAC. Because of the importance of adjuvant chemotherapy, synovial sarcoma must be high on the list of differential diagnoses of high-grade intra-abdominal masses.