Molecular tumor testing for Lynch syndrome in patients with colorectal cancer.

Lynch syndrome (LS) is the most common hereditary colon cancer syndrome, and accounts for 2% to 3% of all colorectal cancers. These tumors are caused by germline mutations of DNA mismatch repair genes, which result in microsatellite instability. Colonic and extracolonic malignancies can occur at a young age, and are often diagnosed at a late stage because of underrecognition of the syndrome.