MLH1 and Lynch syndrome: Germline mutations in the MMR genes MSH2, MLH1, PMS2, and MSH6 are causal for Lynch syndrome, an inherited condition in which patients may develop colorectal cancer (CRC) (constituting ∼3% of all CRCs) and cancers of the rest of the gastrointestinal tract, female reproductive and urinary tracts, and specific skin and CNS tumors (4).