MLH1 and malignant colon neoplasm: Deficiency in MMR genes (dMMR), usually hMSH2 or hMLH1, promotes colon cancer development due to mutation or silencing.[13, 14] dMMR tumors are defined by the accumulation of mutations, mostly insertions or deletions in short tandem repeats throughout the genome.[15] These gene mutations participate in tumor initiation and progression as well as various DNA repair pathways.