MLH1 and colorectal carcinoma: In hypermutated CRC, which accounts for 10–20% of all CRC cases, three quarters are linked to microsatellite instability (MSI CRC) with hypermethylation and silencing of mismatch repair (MMR) genes such as MLH1. MSI CRC is frequently associated with a distinct epigenetic phenotype, including the CpG island methylator phenotype (CIMP).