Hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch syndrome is an autosomal dominant genetic condition that is associated with a high risk of colon cancer as well as other cancers including endometrial cancer (second most common), ovary, stomach, small intestine, hepatobiliary tract, upper urinary tract, brain, and skin. The increased risk for these cancers is due to inherited mutations that impair DNA mismatch repair. It is a type of cancer syndrome. Because patients with Lynch syndrome can have polyps, the term HNPCC has fallen out of favor. Signs and symptoms
Risk of cancer
Lifetime risk and mean age at diagnosis for Lynch syndrome associated cancers

In addition to the types of cancer found in the chart above, it is understood that Lynch syndrome also contributes to an increased risk of small bowel cancer, pancreatic cancer, ureter/renal pelvis cancer, biliary tract cancer, brain cancer, and sebaceous neoplasms. Increased risk of prostate cancer and breast cancer has also been associated with Lynch syndrome, although this relationship is not entirely understood.Two-thirds of colon cancers occur in the proximal colon and common signs and symptoms include blood in the stool, diarrhea or constipation, and unintended weight loss. The mean age of colorectal cancer diagnosis is 44 for members of families that meet the Amsterdam criteria. The average age of diagnosis of endometrial cancer is about 46 years. Among women with HNPCC who have both colon and endometrial cancer, about half present first with endometrial cancer, making endometrial cancer the most common sentinel cancer in Lynch syndrome.
Three or more family members with a confirmed diagnosis of colorectal cancer, one of whom is a first degree (parent, child, sibling) relative of the other two
Two successive affected generations
One or more colon cancers diagnosed under age 50 years
Familial adenomatous polyposis (FAP) has been excludedThe Amsterdam II criteria were developed in 1999 and improved the diagnostic sensitivity for Lynch syndrome by including cancers of the endometrium, small bowel, ureter and renal pelvis.Amsterdam Criteria II (all bullet points must be fulfilled):

Three or more family members with HNPCC-related cancers, one of whom is a first-degree relative of the other two
Two successive affected generations
One or more of the HNPCC-related cancers diagnosed under age 50 years
Familial adenomatous polyposis (FAP) has been excludedThe Bethesda criteria were developed in 1997 and later updated in 2004 by the National Cancer Institute to identify persons requiring further testing for Lynch syndrome through MSI. In contrast to the Amsterdam Criteria, the Revised Bethesda Guidelines use pathological data in addition to clinical information to help health care providers identify persons at high risk.Revised Bethesda Guidelines
If a person meets any 1 of 5 criteria the tumour(s) from the person should be tested for MSI:1. Colorectal cancer diagnosed before age 50
2. Presence of synchronous or metachronous colorectal or other Lynch syndrome associated cancers (e.g. cancers of endometrium, ovary, stomach, small bowel, pancreas, biliary tract, ureter, renal pelvis, brain, sebaceous glands, keratoacanthomas)
3. Colorectal cancer with MSI-high pathology in a person who is younger than 60 years of age
4.