A Case of Malignant Schwannoma of the Transverse Colon

Schwannoma of the digestive tract is rare in the large intestine, especially. Recently we experienced a case of malignant schwannoma of the transverse colon. A 69-year-old male came to our department on 10th, July 1995 because of positive fecal occult blood on medical examination. Barium enema examination revealed an elevated lesion with a broad base and smooth surface, five cm in diameter in the splenic flexure of the transverse colon, so that the lesion was diagnosed as a submucosal tumor. Colonoscopic pictures showed a ulcerated tumor which occupied half of the lumen, and the result of the biopsy was Group 3. This patient was admitted to our hospital on 14th September and transverse colectomy for the submucosal tumor was done on 26th September. At the time of the operation, we suspected that the tumor was a leiomyosarcoma. Histological logical diagnosis of the tumor revealed it to be a 'neurogenic' malignant schwannoma, because immunostaining for s-100 protein showed a positive reaction in the tumor cells, but that for actin showed a negative reaction. Forty-one cases of schwannoma of the large intestine have been reported in Japan between 1939 and 1995, including this case, 11 of which were malignant. In this present study, a case of malignant schwannoma of the large intestine was reported and confirmed histologically, because the reported cases were rare at this time.