Some people inherit a risk for Lynch syndrome (LS), formerly known as hereditary nonpolyposis colorectal cancer. This condition causes 2 to 3 percent of all colon and rectal cancers and usually starts around age 45. Some people with LS develop colon or rectal polyps early in life. People with this condition have an 80 percent risk for colorectal cancer. They’re also more likely to get other cancers, including endometrial, ovarian, stomach, and urinary tract.

LS is caused by mutations in one of the four genes called mismatch repair (MMR) genes.

If preliminary testing of your colon or rectal cancer suggests that may you have LS, a blood test can be performed for further evaluation.

Some patients fit the clinical criteria of LS based on a personal and/or family history of colon and rectal cancer but are found not to have an MMR mutation. These patients are said to have a condition called familial colorectal cancer type X, which may appear similar to LS but can be diagnosed at an older age. Currently, less is known about this syndrome, but patients seem to have an increased risk of colon and rectal cancer and possibly other cancers as well.