KRAS is found mutated in approximately 40% of CRC cases, mainly in the codons 12 (wild-type GGT) and 13 (wild-type GGC) of exon 1, with demonstrated capacity as major predictive markers of resistance to treatment with anti-EGFR monoclonal antibodies in metastatic CRC. This evidence concerns the gene EGFR and colorectal carcinoma.