NRAS and colorectal carcinoma: Mutations of RAS exons outside KRAS exon 2 occurred in 13.9% of CRC patients in our study, of which 8 (2.5%) had single mutations in KRAS exon 3, 29 (8.2%) in KRAS exon 4, and 12 (3.4%) in NRAS exon 2 or 3.