Hereditary Breast Cancer

The most common cause of hereditary breast cancer is a mutation in either the BRCA1 or BRCA2 gene.

Approximately 30% of breast cancer runs in families and has some type of inherited component to it. About 10% of breast cancer cases are due to a specific hereditary cancer syndrome that can be diagnosed by genetic testing (which looks for mutations in specific known genes). This is known as "hereditary" breast cancer.

On the other hand, about 20% of breast cancer cases are due to unknown genetic factors. This means that although the breast cancer does run in the family, there is no specific gene or hereditary cancer syndrome that can be identified to be responsible for the breast cancer in the family. Regardless, individuals in the family are likely at higher risk to develop breast cancer than those without a family history. This is known as "familial" breast cancer.

If you have a family history of breast cancer, a qualified healthcare provider (such as a genetic counselor) can help you to determine whether you are at risk for a hereditary cancer syndrome and might want to consider genetic testing. Even if you are not a candidate for genetic testing (or if testing shows you do not have a hereditary cancer syndrome), you may still be at higher risk for cancer based on other factors, such as your family history of cancer. Learn more about breast cancer risk assessment.

Hereditary Breast Cancer Syndromes

There are various types of hereditary cancer syndromes that lead to an increased risk for breast cancer. The most common cause of hereditary breast cancer is a mutation in either the BRCA1 or BRCA2 gene. Individuals with mutations in these genes have Hereditary Breast and Ovarian Cancer Syndrome (HBOC). Risk factors for this syndrome include any of the following in a patient or their family:

  • Female breast cancer prior to age 50, or at any age, if the patient is of Ashkenazi Jewish descent (Jewish with ancestors from Eastern Europe, usually Germany, Poland, Lithuania, Ukraine and Russia) or if the breast cancer has triple negative pathology
  • Male breast cancer (at any age)
  • Ovarian cancer (at any age)
  • Two or more of these cancers in a person or family (at any age)

Pancreatic cancer can also be associated with HBOC.

Other hereditary cancer syndromes associated with breast cancer risk include, but are not limited to:

  • Cowden syndrome (includes breast, uterine, and thyroid cancer, as well as some other characteristic findings, such as skin manifestations, gastrointestinal polyps, and large head size)
  • Li-Fraumeni syndrome (includes breast cancer, brain cancer, adrenocortical carcinoma, certain types of sarcoma, often at very early ages, possibly even in childhood)

Individuals with a hereditary breast cancer syndrome are at a very high risk to develop breast cancer, as well as other cancers associated with the particular syndrome. As a result, these individuals should undergo different screening and consider different medical management options. Genetic testing is the only way to determine whether someone has a specific hereditary breast cancer syndrome. If a patient is aware of this diagnosis, he or she has the chance to significantly decrease the risk of cancer, if not prevent it completely.

If you think you may have a hereditary breast cancer syndrome in your family, talk to your doctor or visit our webpage about genetic counseling and testing.

Genetic Testing

Cancer genetic testing is a very scientific process. Often patients have many questions about it. Additionally, genetic test results can be complex to interpret. A genetic counselor can help patients understand what the results mean for them and their relatives. A patient who is interested in scheduling a visit with the genetic counselor at Invision Sally Jobe should contact Centralized Scheduling at 720-493-3700. For more information, please view our Frequently Asked Questions about genetic counseling appointments. Patients with general questions can call 720-493-3229 or send an email to

Relevant Resources

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