Pelvic synovial sarcoma of unknown primary origin: case report and literature review.

A case report of a 26-year-old woman with pelvic pain for one-month duration is presented. The physical exam was unremarkable, but a right pelvic mass was found on ultrasound. Computed tomography (CT) of the abdomen/pelvis confirmed a heterogeneous 6 x 4.4 cm mass within the right pelvis adjacent to the superior-lateral aspect of the uterus. Laparoscopy was performed, and the mass was found to be friable and necrotic. The origin of the mass was not able to be determined due to the collapse of the mass upon instrumentation. Histology revealed spindle cells. Further studies, including immunochemical staining, revealed a synovial sarcoma. Patient underwent laparotomy for staging and in hopes of obtaining clear tumor margins. Surgery revealed subsequent tumors involving the mesentery of the small intestine and the peritoneal wall. Biopsies taken at surgery did not reveal the primary origin of the original pelvic tumor.