High Risk Conditions

Hereditary Breast Cancer

Hereditary breast cancer occurs when an abnormal gene is passed from a parent to a child. It accounts for approximately 5-10% of all breast cancer cases.

Having an immediate family member (such as a parent, sibling, or child) with breast cancer can increase your risk of developing the disease. Inherited genetic mutations also raise this risk. The most well-known mutations linked to hereditary breast cancer occur in the BRCA1 (breast cancer gene 1) and BRCA2 (breast cancer gene 2) genes.

Individuals with a BRCA1 or BRCA2 mutation have up to an 85% lifetime risk of developing breast cancer. They are also more likely to be diagnosed at a younger age—often before menopause—and face an increased risk of ovarian cancer. Other genetic mutations, such as PALB2, CHEK2, and ATM, can also contribute to a higher risk of breast cancer.

When to Consider Genetic Testing
Genetic testing may be recommended if you or a family member has experienced:

• Breast cancer diagnosed before age 50
• Triple negative breast cancer (TNBC) diagnosis, especially if diagnosed before age 60
• Multiple relatives on the same side of the family with breast or ovarian cancer
• A relative diagnosed with both breast and ovarian cancer, or cancer in both breasts
• A male family member with breast cancer
• A personal history of multiple types of cancer

Genetic testing guidelines and eligibility criteria vary by province. Speak with your healthcare team to learn what applies to you.

Genetic Testing Process
Genetic testing typically involves analyzing a saliva or blood sample to identify potential mutations. Speak with your healthcare provider to learn more about hereditary breast cancer and whether genetic counseling or testing may be right for you.

For more details, see our advocacy guide: Accessing Genetic Testing in Canada

After a Positive Genetic Test Result
If you receive a positive result for an inherited genetic mutation, your healthcare team can support you in the following ways:

• Screening Plan: You may require more frequent screenings, such as annual mammograms or breast MRIs, to monitor for early changes.
• Risk-Reduction Options: Strategies to lower cancer risk may include:
  • Medications such as Tamoxifen or aromatase inhibitors.
  • Lifestyle changes, including maintaining a healthy weight, exercising regularly, and limiting alcohol consumption.
  • Preventive surgeries, such as mastectomy (removal of breast tissue).
• Personalized Risk Management Plan: Your healthcare provider will create a tailored plan based on your personal and family history.
• Clinical Trials: Participation in research studies may provide access to new prevention strategies or treatments.

Receiving a positive genetic test result can be challenging. Genetic counselors can help you understand your results, explore your options, and navigate the emotional and psychological impact. Sharing your results with family members is important, as they may also be at risk and can take steps to manage their health proactively.

To learn more about how genetic testing affects cancer risk, treatment, and family health, watch our expert-led webinar: Understanding the Role of Genetic Testing

You can also download our Hereditary Breast Cancer Syndrome Factsheet to learn more about hereditary breast cancer, genetic counseling, and resources for support.

Medical Review by Roochi Arora, MD, FRCPC, August 2025

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