Lynch syndrome (LS; also called hereditary nonpolyposis colorectal cancer, HNPCC) is a hereditary cancer susceptibility/predisposition disease caused by a heterozygous germ line mutation in the DNA mismatch repair (MMR) gene MSH2MSH6MLH1 or PMS2[1,2]. This evidence concerns the gene PMS2 and hereditary nonpolyposis colon cancer.