A CASE OF ADENOCARCINOMA LOCATED IN A MIXED HYPERPLASTIC ADENOMATOUS POLYP OF THE COLON

Abstract

A 54-year-old man underwent colonoscopy because of positive occult blood test of stools. A single pedunculated polyp of 1.2 cm in size with irregular surface was found in the ascending colon and easily excised. Most part of the polyp consisted of serrated glands with depletion of goblet cells, characteristic for a hyperplastic colonic polyp. On the top of the polyp, adenocarcinoma is found without adenomatous dysplasia. Malignant transformation of the colonic hyperplastic polyp is scarcely reported. High power view demonstrates goblet cell immaturity, upper zone mitosis, and prominebce of nucleoli, which coincide with mixed hyperplastic adenomatous polyp discribed by Longacre et al. Immunohistochemical study reveals its more resemblance to adenoma than hyperplastic polyp. The mixed hyperplastic adenomatous polyp is supposed to be neoplasm derived from more differentiated cell within the crypt, but its entity and malignant potential are not fully recognized.