KRAS and colorectal cancer: Alternatively, colorectal cancer can be subdivided into five subtypes according to MRR status and detection of BRAF and KRAS mutations; three subtypes are MRR proficient—BRAF-mutant (about 7%), KRAS-mutant (about 35%) and lacking either BRAF or KRAS mutations (49%); and two subtypes are MMR-deficient—the sporadic type with BRAF mutation and/or hypermethylation of MLH1 and the familial type, lacking BRAF mutations or hypermethylation of MLH1 [139].