Lynch Syndrome

Diagnosis

Mayo Clinic specialists run one of the largest and most comprehensive cancer diagnosis and treatment programs in the world, offering advanced screening and diagnostic services. This is especially important for people at risk of Lynch syndrome, a condition that is often challenging to diagnose. An increased understanding of the disorder and advances in molecular technology have made evaluation easier, but identifying individuals and families with Lynch syndrome is still a complex process.

At Mayo Clinic, an evaluation for Lynch syndrome begins with a careful review of your family history. The next step, especially for people who develop cancer before age 50, is usually a tumor test, a preliminary strategy to help determine which patients should be offered genetic testing.

Tumor testing

Tumor tests are performed on a sample of colon, endometrial or other cancer tissue that has been frozen and stored after surgery. The tests can't confirm that you have Lynch syndrome, but a positive test result does indicate that mutations exist in the genes responsible for the disorder. Tumor tests used at Mayo Clinic include:

• Immunohistochemistry: For at-risk people who have had cancer surgery, Mayo Clinic pathologists stain tumor samples and examine them for proteins normally produced by DNA repair genes. A missing protein is a sign of a defect in the genes. The Immunostains laboratory at Mayo Clinic is staffed by a team of highly experienced scientists and performs nearly 1,000 immunohistochemical tests every day.
• Microsatellite instability testing: Microsatellites are repeated sequences of DNA. Normally, every person has microsatellites of a certain length. But in people with defects in the DNA repair genes — the genes associated with Lynch syndrome — the DNA sequences become longer or shorter than usual, a condition known as microsatellite instability. The great majority of people with Lynch syndrome test positive for microsatellite instability. The test isn't specific for a particular gene, however, and it can't distinguish between cancers that are inherited and those that occur for other reasons.

Genetic testing

Based on the results of tumor tests, Mayo Clinic physicians may suggest that you consider genetic testing. Performed on a small blood sample, a genetic test looks for the specific gene abnormalities that cause Lynch syndrome. Although not perfect, gene testing is the best way to diagnose the disorder. Mayo Clinic has one of the most distinguished medical genetics programs in the country as well as state-of-the-art cytogenics, biochemical and molecular laboratories.

The results of the gene test help determine the best course of care for you and your family. A positive test means that you have inherited the genetic abnormality that causes Lynch syndrome, and you will need lifelong monitoring for colorectal and other cancers. Your family members will also be encouraged to discuss genetic testing with a Mayo Clinic counselor.

You are not obligated to undergo genetic testing, and it shouldn't be undertaken without careful consideration. Before you make a decision, a Mayo Clinic genetics counselor will discuss all the ramifications of testing with you, including the accuracy, medical usefulness and limitations of genetic tests; the psychological and medical implications for you and your family; and confidentiality issues. Patients who choose to be tested discuss the test results with their counselor.