Breast cancer risk factors

Woman holding illustration of healthy breast tissue. What are breast cancer risk factors?

Last month, we looked at two different types of genetic variants: BRCA variants and the KRAS-variant. Both BRCA and KRAS are pathogenic variants that are linked to an increased risk of breast cancer. In this month’s blog post, we’re going to dive into the general accepted breast cancer risk factors.

To give you a high level overview, breast cancer occurs when a breast cell begins to grow abnormally, divide rapidly, and accumulate, forming a lump or mass. Your risk for breast cancer is due to a combination of factors – hormonal, environmental, and lifestyle factors. While the list below might make you uneasy, don’t panic! Most women have some risk factors, but that doesn’t necessarily mean you will get breast cancer. Yet, some women will still get breast cancer even with only having a few of these known risk factors.

General accepted breast cancer risk factors

50+ Female

  • Most breast cancers are found in women over 50 years old – age is the main factor that influences your risk of breast cancer.

Genetic variants

  • As we learned from the last blog post, those with certain genetic variants, like BRCA variants and the KRAS-variant, have an increased breast cancer risk
    • BRCA1 is 55%–72%*
    • BRCA2 is 45%–69%*
    • The KRAS-variant is 25%-30%

A personal history of breast conditions

  • Extra cell growth in the breast, such as lobular carcinoma in situ (LCIS)iAn uncommon condition in which abnormal cells form in the milk glands (lobules) in the breast. or atypical hyperplasiaiAn accumulation of abnormal cells in the milk ducts and lobules of the breast, considered a precancerous condition. is linked to an increased risk of breast cancer.

Family history of breast cancer

  • While the majority of those diagnosed with breast cancer have no family history, if your mother, sister, or daughter was diagnosed with either breast or ovarian cancer, you are at increased risk.

Reproductive history

  • Never being pregnant, never breastfeeding, or giving birth to your first child after age 30 puts you at a higher risk.

Period and Menopause timing

  • You have a higher risk if you begin your period before age 12 and begin menopause at an older age.


  • Obesity is associated with an increased breast cancer risk.

Physical Activity

  • Lack of physical activity can add to your risk.

Alcohol consumption

  • Studies show that your breast cancer risk increases with excessive alcohol consumption.

You may have noticed we left Hormone Replacement Therapy (HRT) off of this list of breast cancer risk factors. In next month’s blog post, we’re going to try to address some of the confusion around HRT and its role, if any, in breast cancer risk. 

Do you have any questions about breast cancer risk factors? Leave us a comment below or if you’d like to keep it private, email us at


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