MLH1 and cancer: The condition is caused by a pathogenic variant (PV) in one of the four mismatch repair (MMR) genes: MLH1, MSH2, MSH6, PMS2 or by epigenetic silencing of MSH2 through deletions in EpCAM. 1These variants compromise the DNA MMR system, resulting in an increased accumulation of replication errors and, consequently, a substantially elevated risk of cancer.1