MLH1 and colorectal carcinoma: The mutation or hypermethylation of mismatch repair genes (MutL Homolog 1 [MLH1], MutS Homolog 2 [MSH2], MSH6, or PMS2) leads to deficient mismatch repair (dMMR) and causes error accumulation in DNA sequences, thus increasing the risk of CRC and other epithelial cancers [5].