Colonic intra-epithelial carcinoma occurring in a hyperplastic polyp via aserrated adenoma

We present a case of intra-epithelial carcinoma occurring in a serrated ade noma of the colon. The pedunculated polyp, which measured 12 x 10 x 6 mm, w as endoscopically removed from the ascending colon of a 78-year-old woman. Histologically, the polyp mainly consisted of serrated adenomatous glands, and had foci of intra-epithelial carcinoma at the top. Hyperplastic (metapl astic) areas were also present in both borders between the serrated adenoma tous area and the surrounding normal mucosa. A sequential increase in the d egree of dysplasia, and in the number of nuclei positively reactive for Ki- 67 and p53 was evident from the hyperplastic areas toward the foci of carci noma. The polyp described here may represent a carcinogenic potential of hy perplastic polyp via serrated adenoma.