LAUSR

Study Objective Synovial sarcoma most commonly presents as a soft tissue tumor in young adults. This case report illustrates a diagnostic dilemma, in which a rare tumor was misdiagnosed on imaging on two separate occasions as common gynecological pathologies. Design N/A Setting N/A Patients or Participants N/A Interventions N/A Measurements and Main Results 45-year-old woman presented to the GynOncology clinic as a referral for management of a pedunculated leiomyoma identified on MRI. The patient was counseled on options, and agreed to placement of an intrauterine device. She re-presented two years later, and pelvic ultrasound showed that the previously identified fibroid was now believed to be a dermoid cyst; with interval increase in size, measuring 10.6 × 12.1 × 15. The patient underwent diagnostic laparoscopy, where a mass of indeterminate origin was noted; involving the round ligament, broad ligament, abdominal peritoneum, and abutting the dome of the bladder. Intraoperative frozen section returned indeterminate. Given the patient's desire for future fertility and uncertainty of malignancy, the decision was made to await final pathology before proceeding with surgical management. Pathology showed low-grade spindle-cell sarcoma with molecular features of synovial sarcoma. In two weeks time, the patient underwent a robotic-assisted total laparoscopic hysterectomy, bilateral salpingo-oophorectomy, and tumor debulking. Per the operative report, the mass that was first thought to be a pedunculated fibroid and then a dermoid cyst was an approximately 20cm retroperitoneal mass originating from the left broad ligament and occupying the entire left pelvic sidewall, pararectal space, paravesical space, and the space of Retzius and encasing the left ureter. Final pathology showed synovial sarcoma, which was confirmed with FISH results. Conclusion This case demonstrates synovial sarcoma misdiagnosed as common gynecological pathologies. This rare pathology is one that gynecologists should be aware of, as its early recognition and treatment allows for improved survival benefit with adjuvant chemotherapy.