Serrated adenomatous polyposis in humans

Background & Aims: Hyperplastic polyposis clinically resembles adenomatous polyposis and has not generally been considered precancerous. However, since the original description, a number of cases associated with adenocarcinoma have been reported. The aim of this study was to reevaluate patients previously diagnosed with hyperplastic polyposis. Methods: Pathological analysis of polyps in 6 patients with putative hyperplastic polyposis and 4 with associated carcinoma was compared with classic isolated hyperplastic polyps, adenomas, and solitary serrated adenomas. Immunohistochemical study for the detection of p53 protein, blood groups antigens, including Lewis(a) and Lewis(b), and peanut lectin binding was performed. Results: Polyps in our patients were much more similar to serrated adenomas than to hyperplastic polyps and were characterized by large size, prominent architectural distortion, cytologically atypical nuclei, focal nuclear crowding and nuclear dispolarity, and rare upper zone mitotic figures. The polyps in our patients and control serrated adenomas had a decrease or absence of endocrine cells compared with classic hyperplastic polyps and normal colon and similar immunohistochemical reactivity for p53 and Lewis(a) and Lewis(b) antigens. Conclusions: Our results indicate that the polyps in our patients are serrated adenomas. Serrated adenomatous polyposis has not been described before and should be distinguished from true hyperplastic polyposis given a possible association with adenocarcinoma in the former group.