Our data confirms the Vogelstein's theory of gradual accumulation of mutations, especially in the driver genes, such as APC, TP53 and KRAS. The set of adenomas and in situ carcinomas only very rarely exhibited MSI-H phenotype and the role of mutations in POLE and PI3KCA genes in adenoma to carcinoma transition warrants further investigations. This evidence concerns the gene KRAS and in situ carcinoma.