KRAS and rectal cancer: In this study, we investigated the mutation status of KRAS (exons 2, codon 12/13), NRAS (exons 2/3/4, codon 12/13/59/61/117/146) and BRAF (exons 15, codon 600) in 260 patients, including 86 cases of colon cancer, 140 cases of rectal cancer and 34 cases of gastric cancer.