Lynch syndrome, or hereditary nonpolyposis colorectal cancer (HNPCC), is an autosomal dominant genetic syndrome that predisposes individuals to multiple cancer types and is caused by germline mutations in one of the mismatch repair genes, usually MLH1 (human MutL homolog 1), MSH2 (MutS protein homolog 2), MSH6 (MutS protein homolog 6), or PMS2 (PMS protein homolog 2) [1]. This evidence concerns the gene MLH1 and hereditary nonpolyposis colon cancer.