Lynch syndrome (LS) is the most common hereditary colorectal cancer syndrome and accounts for ~3 % of all CRCs. This autosomal dominant disorder is caused by germline mutations in DNA mismatch repair genes (, and ). One in 300 individuals of the general population are considered to be mutation carriers (300 000 individuals/Germany). Mutation carriers are at a high CRC risk of 15-46 % till the age of 75 years. LS also includes a variety of extracolonic malignancies such as endometrial, small bowel, gastric, urothelial, and other cancers.