KRAS and hyperplastic polyp: KRAS mutation was present in 22 cases including 1 hyperplastic polyp, 1 sessile serrated adenoma without intraepithelial neoplasia, 2 sessile serrated adenomas with high grade intraepithelial neoplasia, 9 traditional serrated adenomas with low grade intraepithelial neoplasia, 1 traditional serrated adenoma with high grade intraepithelial neoplasia and 8 invasive serrated adenocarcinomas.