BRAF is a downstream molecule of KRAS. Although more than 40 somatic mutations in the BRAF kinase domain have been described, the most common mutation across various cancers is the classic GTG → GAG substitution at the position 1799 of exon 15, which results in the V600E amino acid change, and the subsequent constitutive activation of the EGFR signalling pathway. The gene discussed is KRAS; the disease is cancer.