What Is Lynch Syndrome?

genetic counseling session

Lynch syndrome is a hereditary condition that can increase risk for certain cancers. Meeting with a genetic counselor can help patients understand and manage risk.

Lynch syndrome, also known as hereditary nonpolyposis colorectal cancer (HNPCC), is the most common hereditary form of colorectal cancer. In the United States, about 140,000 new cases of colorectal cancer are diagnosed each year and approximately 3 to 5 percent of these cancers are caused by Lynch syndrome.

Individuals with Lynch syndrome have a 50 to 80 percent lifetime risk of developing colorectal cancer compared to 2 percent in the general population. Women with Lynch syndrome also carry a 40-60 percent lifetime risk of developing endometrial cancer.

In addition to higher colorectal and endometrial cancer risk, individuals with Lynch syndrome also carry an increased risk of developing cancers of the stomach, small intestine, pancreas, liver, gallbladder ducts, upper urinary tract, brain, and skin. Women with the syndrome also have a higher risk for ovarian cancer.


What Causes Lynch Syndrome?

Lynch syndrome is caused by a germline mutation in DNA repair genes, also known as the mismatch repair genes. A germline mutation is a change in the DNA that can be passed to children and affect generations of a family.

The mismatch repair genes are MLH1, PMS2, MSH2, MSH6 and EPCAM. About 80 percent of people with Lynch syndrome have an alteration in either the MLH1 or MSH2 gene, and alterations in the MSH6 gene are responsible for about 5 to 10 percent. Other genes that have been linked to Lynch syndrome include PMS2 and EPCAM.


Who Is at Risk for Lynch Syndrome?

If colorectal or endometrial cancer run in your family, it’s possible the gene mutation that causes Lynch syndrome has been passed down.

If you believe you may be at risk, speak with a doctor about potential genetic testing and steps for prevention.

lynch syndrome pedigree

A pedigree showing some of the classic features of a family with Lynch syndrome across three generations, including transmission occurring through maternal and paternal lineages and the presence of both colon and endometrial cancers. Credit: National Cancer Institute.


How Is Lynch Syndrome Managed?

Regular screening can help detect early stages of cancer and some preventive measures can lower risk of certain cancers. There are a variety of monitoring and treatment options available:

Colorectal cancer:

  • Regular colonoscopies can effectively screen for the development of colorectal cancer and help diagnose it in its earlier, and more treatable, stages.
  • Some individuals also consider removing the colon as a preventive measure. Any type of surgery requires careful consideration of the risks and benefits and should be discussed with your care team.
  • While it isn’t certain, studies have shown that some people with Lynch syndrome who take high doses of aspirin daily for more than two years may have a reduced risk of Lynch syndrome-associated cancer.

Endometrial cancer:

  • Because the screening for endometrial cancer has not been proven to be very effective at detecting early cancer, women with Lynch syndrome may consider removal of the uterus (and sometimes ovaries) after they have completed their families and are physically and emotionally ready.
  • For those women with Lynch syndrome who are not ready to have preventative surgery, they should keep an eye out for any irregular or unusual vaginal bleeding, as that can indicate the early development of cancer. Oftentimes doctors will offer an annual pelvic ultrasound and endometrial biopsy beginning at 35.
  • Oral contraceptives may also aid in cancer prevention.

Screening for other Lynch syndrome associated cancers include:

  • Annual skin examinations
  • Endoscopy of the upper gastrointestinal tract
  • Annual urine tests

If you or a family member is diagnosed with Lynch syndrome, it’s important to speak with your doctor to find a prevention plan that’s right for you. Dana-Farber Cancer Institute’s Center for Cancer Genetics and Prevention includes a team of expert clinicians who provide risk assessment and comprehensive recommendations for managing cancer risk.


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