[Schwannoma originating from the obturator nerve with suspicion of lymph node metastasis].

A 58-year-old man, received polypectomy to evaluate the polyp of sigmoid colon. Pathological examination of the specimen revealed non-invasive adenocarcinoma. Systemic work up including abdominal computed tomography (CT) demonstrated a bladder tumor 11 x 18 mm in diameter associated with left obturator lymph node swelling (16 x 14 mm). In the preoperative staging, this nodule was suspected to be lymph node metastasis, even though both cancers were diagnosed to be early stage. Transurethral resection of bladder tumor (TUR-Bt) and lymph node open biopsy were performed. The final diagnosis of bladder tumor was pTa, urothelial cancer grade 2 and low grade. The nodule had originated from the obturator nerve itself, and pathological diagnosis demonstrated benign schwannoma. To the best of our knowledge, this is the 14th report of benign schwannoma of the obturator nerve in Japan.