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Diagnosis Cancer

Lynch Syndrome

If you have a family history of cancer, it is extremely important that you let your doctor know. Your doctor will then take a thorough recording of your family history, paying particular attention to cancer diagnoses. If your doctor suspects that you may have Lynch syndrome, they will refer you to a health care professional who specializes in genetic cancer screening, testing and counseling.

In addition, all newly diagnosed colorectal cancer or endometrial cancer patients also should be screened or tested for Lynch syndrome.

Genetic Testing

Genetic testing involves a simple blood test. Your blood sample is sent to a special laboratory where it is analyzed for certain changes or mutations that indicate Lynch syndrome.

If you test positive for Lynch syndrome, meaning that genetic mutations were found in your blood, this does not necessarily mean that you will get cancer. It means that your lifetime risk of developing colon cancer is between 60 to 80 percent. You also have an increased chance of developing other cancers associated with Lynch syndrome.

A negative test result for Lynch syndrome, meaning that genetic mutations were not found in your blood, depends on additional factors such as whether your family members have Lynch syndrome or colon cancer. If you test negative for Lynch syndrome but have family members with the syndrome, your risk for colon cancer is not increased, but remains the same as the general population. However, in some cases, such as if you have a strong family history of colon cancer, a negative test result may still mean that you are at an increased risk for colon cancer.

Your genetic counselor will explain your test results and help you make decisions regarding cancer prevention, screening and treatment options.

Who Should Be Screened or Tested

Based on established medical criteria, the following people should be screened or tested for Lynch syndrome:

  • Newly diagnosed colorectal or endometrial cancer patients The first step in Lynch syndrome diagnosis is evaluating your tumor for molecular features associated with Lynch syndrome. When a tumor is not available for screening, DNA blood testing can be done if your family history and cancer diagnosis strongly suggest Lynch syndrome. UCSF's Cancer Genetics and Prevention Program, in conjunction with our Gastrointestinal Cancer Prevention Program, offers a unique service to all colorectal cancer and endometrial cancer patients. We automatically screen patients' tumors for Lynch syndrome at the time of their surgery for colorectal or endometrial cancer. Patients who screen positive are then referred for genetic counseling and testing.
  • Patients diagnosed with more than one Lynch syndrome-related cancers If you have been diagnosed with multiple cancers associated with Lynch syndrome including colorectal, endometrial, ovarian, gastric, small bowel, upper urinary tract, hepatobiliary tract, pancreas, brain and sebaceous neoplasia of the skin, you should be screened or tested for Lynch syndrome.
  • Patients with a family history of colorectal or endometrial cancer If you have two or more relatives with colorectal or endometrial cancer, particularly if one was affected before age 50, you should be screened or tested for Lynch syndrome.

UCSF Health medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your provider.