MLH1 and hereditary nonpolyposis colon cancer: The first is the nonpolyposis (hereditary nonpolypoid colon cancer (HNPCC) with its two types: Lynch I & II), which is an autosomal dominant disease that occurs due to mutations in the DNA mismatch repair (MMR) genes MLH1, MSH2, MSH6 and PMS2 which is known to be positive in around 1%–3% in the West, meanwhile it is 4.7% in Iran for example!