Lynch syndrome is an inherited cancer predisposition condition caused by a mutation in one of the four mismatch repair (MMR) genes MLH1, MSH2, MSH6, and PMS2. Mutations cause a significantly increased risk of a number of cancers.
Lynch syndrome was previously known as Hereditary Non‐Polyposis Colon Cancer (HNPCC)
People with Lynch syndrome have a significantly higher risk of colorectal and endometrial cancers. Other cancers seen less frequently in Lynch syndrome include ovarian, gastric, biliary/pancreatic, urothelial, small bowel, brain, and sebaceous adenomas/carcinomas. Recent studies suggest there may also be an increased risk of developing breast or prostate cancer. Personal risks may differ based on what type of genetic fault is involved.
Lynch syndrome is extremely under‐diagnosed. Although Lynch syndrome is identified in approximately 3% of all colorectal cancers (CRCs), it is estimated that >90% of Lynch syndrome carriers are unaware of their Lynch syndrome status. These carriers are therefore unaware of their increased cancer risk and surveillance needs and cannot alert their families.