MMR IHC assesses the presence or absence of the four routinely evaluated MMR proteins (MSH2, MSH6, MLH1, and PMS2) in cancer cells as well as EPCAM, since the deletion of heterozygous sequences at the 3’ end of EPCAM can result in MSH2 inactivation in EPCAM-expressing tissues by causing the promoter hypermethylation of MSH2 [28,29]. The gene discussed is MSH2; the disease is cancer.