By Miriam Komaromy, MD

Reviewed By Peggy Conrad, MS, CGC and Jonathan Terdiman, MC
Last Updated August 1, 2000

Although colon cancer is the disease most frequently associated with the hereditary syndrome hereditary nonpolyosis colorectal cancer (HNPCC, also known as Lynch Syndrome), people who have inherited this condition are also at increased risk for a number of other types of cancers. Researchers, in fact, are still trying to identify all of the cancers that might be connected to HNPCC.

Uterine and Ovarian Cancer

For women, HNPCC poses a couple of special risks — namely uterine and ovarian cancer.

Uterine cancer. Although 3 percent of women in the general population will be diagnosed with uterine cancer at some point in their lives, approximately 40 percent of women with HNPCC will develop this disease. Even though HNPCC is usually thought of as a hereditary colon cancer syndrome, uterine cancer is common enough in HNPCC that some families will have several cases of uterine cancer and few or no cases of colon cancer.

Ovarian cancer. Although only approximately 1.5 percent of women in the general population will develop ovarian cancer over the course of their lives, approximately 10 percent of women with HNPCC will eventually develop this disease.

Stomach Cancer

Rare Cancers

In addition to the cancers mentioned above, HNPCC puts people at increased risk for a number of other, more rare forms of cancer. However, the risk for these is much lower. Less than five percent of individuals who have inherited HNPCC will develop any of these malignancies over the course of their lifetimes.

The most common of these additional HNPCC-associated cancers are cancer of the small bowel, cancer of the urinary tract, cancer of the gall bladder and bile ducts, and brain cancer.

In addition, scientists have recently linked a condition called Turcot's syndrome to both HNPCC and familial adenomatous polyposis (FAP), another hereditary syndrome associated with colon cancer. Although scientists have long known about the existence of Turcot's syndrome — which is characterized by the presence of colon cancer and brain cancer in a single family — they did not understand until recently that it could be connected to HNPCC and another well-characterized hereditary colon cancer syndrome called familial adenomatous polyposis (FAP).

Aarnio, M., J.-P. Mecklin, et al. (1995). Lifetime risk of different cancers in hereditary nonpolyposis colorectal cancer (HNPCC) syndrome. Int J Cancer. 64: 430-33.

Vasen, H. F. A., J. T. Wijnen, et al. (1996). Cancer risk in families with hereditary nonpolyposis colorectal cancer diagnosed by mutation analysis. Gastroenterology. 110: 1020-1027.

Dunlop, M., S. Farrington, et al. (1997). Cancer risk associated with germline DNA mismatch repair gene mutations. Hum Mol Genet. 6: 105-110.