RESUMEN
Ulcerative colitis is a chronic inflammatory bowel disease manifested by diffuse continuous mucosal and submucosal inflammation. Adenocarcinoma of the colon may be complicated in the long-standing, extensive ulcerative colitis. But the case of an atypical carcinoid tumor arising in the chronic ulcerative colitis has been very rarely reported. A case was experienced involving a 54-year-old woman with chronic ulcerative pancolitis that was complicated by an atypical carcinoid tumor of the sigmoid colon. A small, flat, elevated lesion was found at the sigmoid colon, 8 years after the initial diagnosis of ulcerative colitis had been made. The microscopic finding of the lesion showed the nest of moderately differentiated, medium sized cells with large nuclei. The immunohistochemical stains for cytokeratin, NSE, chromogranin A, and synaptophysin were positive.The patient was treated with a total colectomy accompanied with an ileostomy, and is now in a very favor able state of recovery.