Hereditary non-polyposis colorectal cancer (Lynch syndrome)Hereditary non-polyposis colorectal cancer (HNPCC) is characterised by an increased risk of colorectal cancer and also cancers of the endometrium, ovary, stomach and small intestine.It is an autosomal dominant condition caused by a mutation in one of the DNA mismatch repair genes. The most commonly affected genes are MLH1 and MSH2. The lifetime risk of developing colorectal cancer is 80%, and the mean age of diagnosis is 45 years. Most cancers develop in the proximal colon. Females have a 30-50% lifetime risk of developing endometrial cancerRef: Bailey and Love, 27e, page: 1260