Hereditary non-polyposis colon cancer, also known as Lynch syndrome, accounts for about 3% to 5% of all colorectal cancers. HNPCC can be caused by inherited changes in a number of different genes that normally help repair DNA damage.
This syndrome develops when people are relatively young. People with HNPCC have polyps, but they only have a few, not hundreds as in FAP. The lifetime risk of colorectal cancer in people with this condition may be as high as 80%.
Women with this condition also have a very high risk of developing cancer of the endometrium (lining of the uterus). Other cancers linked with HNPCC include cancer of the ovary, stomach, small bowel, pancreas, kidney, brain, ureters (tubes that carry urine from the kidneys to the bladder), and bile duct.