Genetic Testing

Although many people who have a family history of cancer worry about hereditary risk, most cancers – even those within a single family – occur simply by chance. In fact, only 5 to 10 percent of cancers are linked to inherited genetic mutations (abnormalities).

However, tests now exist to identify many of the mutations that cause rare inherited cancer syndromes. Geneticists have identified more than 50 of these hereditary cancer syndromes.

Before you decide to be tested, talk to your doctor about genetic counseling, which is recommended both before and after having a genetic test. A genetic counselor can help you make an informed decision about whether to have genetic testing by educating you on the risks and benefits and explaining how testing will affect you and your family.

As someone who has finished cancer treatment, it is important for you to note if other family members are diagnosed with the same cancer in the future. If this occurs, your family will be a candidate for genetic testing. This is important for you and your family members’ doctors to have in the medical records.

Testing is usually requested by a doctor and may be performed on a small sample of fluid or tissue — usually blood, but sometimes saliva, amniotic fluid or a swab of cells from inside your cheek. After being examined at a laboratory, the results are sent back to the doctor and/or genetic counselor or directly to you. At-home or direct-to-consumer genetic tests are available; however, they may detect common genetic variants rather than identifying known hereditary cancer syndromes, and their results may be hard to interpret without the advice of a trained genetic counselor.

Many health care professionals recommend testing only when there is reason to believe a person might have a hereditary cancer syndrome; the test is likely to give clear, accurate results; or the results are likely to be useful for planning treatment or medical care.

After testing, a genetic counselor can help you to interpret the results and use them to plan future health care. If a genetic mutation is identified, your genetic counselor may discuss options to reduce your risk, including earlier or more frequent screenings, lifestyle changes or preventive treatments. Your doctor may strongly encourage you to share the results of genetic testing with your family. A positive result may confirm a hereditary cancer syndrome and/or indicate a higher chance of a mutation in a first-degree relative (sibling, child or parent). Understanding your results will allow family members to make more informed decisions about their own health care and lifestyle. It’s important to remember, however, that a positive result for a hereditary cancer syndrome does not mean the person who inherits the mutation will get cancer.


Common Hereditary Cancer Syndromes

Cowden syndrome (PTEN hamartoma tumor syndrome)
  • Gene: PTEN
  • Cancer types: breast, thyroid, uterine
Familial adenomatous polyposis
  • Gene: APC
  • Cancer types: bone, colorectal, skin, small intestine, stomach; brain tumors
Hereditary breast cancer and ovarian cancer syndrome
  • Genes: BRCA1, BRCA2
  • Cancer types: breast, pancreatic, prostate, ovarian
Li-Fraumeni syndrome
  • Gene: TP53
  • Cancer types: adrenal, brain, breast, leukemia, osteosarcoma, soft tissue sarcoma
Lynch syndrome (hereditary nonpolyposis colorectal cancer)
  • Genes: EPCAM, MLH1, MSH2, MSH6, PMS2
  • Cancer types: brain, breast, colorectal, liver, ovarian, pancreatic, renal pelvis, small intestine, stomach, uterine
Von Hippel-Lindau syndrome
  • Gene: VHL
  • Cancer type: kidney



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