MLH1 and cancer: It may be caused by pathogenic variants of mismatch repair (path_MMR) genes, and usually four DNA MMR genes including path_MSH2, path_MLH1, path_PMS2, or path_MSH6 are collectively refers to path_MMR. New evidence proved that genetic subgroups are at risk for different cancers in aging population and these cancers have very different prognoses.