The 26 cases without BRAF and KRAS mutation were comprised of 1 hyperplastic polyp, 7 sessile serrated adenomas without intraepithelial neoplasia, 2 sessile serrated adenomas with low grade intraepithelial neoplasia, 1 sessile serrated adenomas with high grade intraepithelial neoplasia, 2 traditional serrated adenomas with low grade intraepithelial neoplasia, 4 traditional serrated adenomas with high grade intraepithelial neoplasia and 9 invasive serrated adenocarcinomas. This evidence concerns the gene KRAS and intraepithelial neoplasia.