The genetic and epigenetic alterations that lead to colorectal carcinogenesis can be grouped into three major pathways: traditional pathway (MSS, CIMP-negative, and/or wild type BRAF and KRAS), serrated pathway (MSI or MSS, CIMP-positive, BRAF mutation), and alternate pathway (MSS, CIMP-low, KRAS mutation). This evidence concerns the gene KRAS and medical procedure.