Immunohistochemical (IHC) and genetic studies of rectal cancer do not differ from CRC studies and include routine hematoxylin–eosin staining; evaluation of the expression of cytokeratins CK8/18 and CK20, as well as CDX2; and the revelation of activating mutations in proto-oncogenes such as KRAS, NRAS, and BRAF, along with evaluation of the status of microsatellite instability (MSI) [5]. Here, KRAS is linked to rectal cancer.