A Case of Giant Retroperitoneal Schwannoma Originating from the Sciatic Nerve Resected with the Transsacral Approach

Abstract

Schwannoma occurs rarely in the retroperitoneum. The tumors can attain large sizes and cause surgical difficulties. The patient was a 43-year-old male who was incapacitated by a large pelvic tumor, associated with abdominal pain. The neurologic examination was unremarkable. MRI scan showed a 13 x 10 x 8 cm mass with a high signal on T2-weighted images. The stalk of the tumor continued to the left S4/5 intervertebral foramen. The patient underwent surgery with suspicion of schwannoma arising from the retroperitoneum. First, we separated the tumor from the sacral bone and sacral vessels by the transsacral approach in the prone position. Next, the patient was changed to the dorsosacral position. A huge retroperitoneal tumor was seen, however, we could separate the tumor from adjacent tissue with the caudal dissection line as a guide. The tumor was excised intact within its fibrous capsule. HE stain showed Antoni A type with a palisade arrangement of cells. On immunohistochemistry, the tumor was positive for S-100 proteins. Finally, the patient was diagnosed with retroperitoneal schwannoma.