NRAS and colorectal cancer: Activating mutations in exons 2 (codons 12 and 13), 3 (codons 59 and 61) and 4 (codons 117, 126 and 146) of the NRAS gene have been frequently described in melanoma (13–25%), myeloid leukemia (10%), colorectal cancer (2–5%), hepatocellular carcinoma (1.4%) and thyroid carcinoma (6%) [31].