KRAS and metastatic colorectal cancer: Scholars advocate molecular staging, such as through immunohistochemistry, for all colon cancers as well as detection of mismatch repair defects (MMR-D) or microsatellite instability high (MSI-H) through polymerase chain reaction to screen for Lynch syndrome and mutations in KRAS, NRAS, and BRAF in metastatic colorectal cancer (Biller and Schrag, 2021).