Testing for KRAS, NRAS exon 2, 3, and 4, and BRAF V600E mutations as part of the work-up for confirmed CRC in the metastatic setting is recommended by the National Comprehensive Cancer Network (NCCN) guidelines, the European Society for Medical Oncology (ESMO), and the Pan-Asian adapted ESMO consensus guidelines, and all patients with CRC (including those with localized status) are tested for MSI [7,59,60,61,62]. The gene discussed is KRAS; the disease is colorectal carcinoma.