Content courtesy of my friend at Myriad Mr. Brandon Deck. For more information see their website at http://www.myriadtests.com Lynch Syndrome or hereditary non-polyposis colorectal cancer (HNPCC) is the most common hereditary colorectal cancer (CRC) syndrome comprising about 3% to 5% of all CRCs. About 1 in 660 to 1 in 2000 individuals have Lynch syndrome making it just about as common as hereditary breast and ovarian cancer (HBOC) syndrome. However Lynch syndrome is even more under diagnosed than hereditary breast and ovarian cancer syndrome.