NRAS and rectal cancer: NRAS mutations were detected in 6 out of 140 (4.3%) rectal cancer samples (Table 2, Figure 2B), of which 3 (2.1%) samples had mutations in exon 2 codon 12, 2 (1.4%) samples had mutations in exon 2 codon 13, and 1 (0.7%) sample had mutations in exon 3 codon 61 (Table 3).