Granular cell tumor of the ascending colon: a case report.

A granular cell tumor (granular cell myoblastoma) of the ascending colon in a 48-year old male is reported. The tumor was detected by barium enema study as a sessile polyp, and colonofiberscopy revealed submucosal tumor. It was removed by endoscopic polypectomy. Macroscopic examination showed the characteristic features of granular cell tumor. The avidin-biotin-peroxidase complex (ABC) method for detection of S-100 protein demonstrated that the cytoplasm of tumor cells and the pleomorphic nuclei were strongly stained with anti-S-100 protein serum, which supports the concept of the Schwann cell origin of granular cell tumor.