Abstract
A 71-year-old woman had indications of rectal cancer on endoscopy during surveillance for recurrent/slowly-developing ulcerative colitis (total colitis type) that had lasted 23 years. Contrast-enhanced computed tomography (CT) and MRI showed a 15-mm tumor in the left lateral lymph node region, and left lateral lymph node metastasis was suspected. She was diagnosed with ulcerative colitis-related rectal cancer, T3N3M0, Stage IIIb, and underwent a left lateral dissection along with laparoscopic total colectomy and ileal pouch-anal anastomosis, during which a somewhat round tumor that was enlarged in a fusiform manner so as to be continuous with the obturator nerve was observed ; the obturator nerve was severed, and the tumor was excised. Histopathological findings were positive for S-100 on immunostaining, with an MIB-1 index of 1.6%, and no atypical mitotic figures were observed. She was therefore diagnosed with a benign schwannoma predominantly of the Antoni A type. She had no neurological symptoms of the left lower limb that interfered with ADL postoperatively. Retroperitoneal schwannoma in the obturator nerve is very rare and is discussed along with a review of the literature.
