Serrated adenoma of the colorectum: colonoscopic and histologic features

Background: Serrated adenoma is a recently recognized epithelial neoplasm of the colorectum. The aim of this study is to clarify the colonoscopic features of serrated adenomas. Methods: The endoscopic findings for 52 serrated adenomas of the colorectum were investigated; these were then divided into three groups according to surface features. The histologic type (tubular, tubulovillous or villous) and the incidence of high-grade dysplasia were compared among the three groups. Results: The surface under chromoscopy showed a hyperplastic pattern in 17 lesions,a cerebriform pattern in 18 lesions and a combined pattern in 17 lesions. The tubular type of serrated adenoma was predominant in the hyperplastic pattern group (94%), whereas the tubulovillous or villous histologic types were frequent in the cerebriform pattern (89%) and combined pattern (82%) groups. nigh-grade dysplasia was found in 18% of the combined pattern adenomas; the incidence was lower in hyperplastic (6%) or cerebriform pattern (0%) adenomas. Conclusions: Surface features of serrated adenomas have a close correlation with their histologic type. A combined hyperplastic-cerebriform surface pattern under chromoscopy was seen only in serrated adenomas.