KRAS and colorectal carcinoma: Hence, our findings confirm previous evidence that mutations at codons 12 and 13 (G13D, G12D, and G12V) of the KRAS gene are the most frequent mutations in stage I CRC [6–8, 17, 18], while NRAS, BRAF, and PIK3CA mutations are rare in this subgroup of CRC [6–8, 17].