KRAS and colorectal carcinoma: The combination and sum of these alterations lead to a genetic classification of CRC carcinogenesis, and two phenotypes can be identified: [1] The CIN phenotype (65–70%) is related to defects in chromosomal segregation, telomeric stability and mutations in APC, KRAS and TP53; [2] MSI phenotype (15%), which are hypermutated as a result of a defective DNA mismatch repair (MMR) system.