Breast Cancer Causes

While researchers are still unsure of exact breast cancer causes, some risk factors are associated with the disease. Because these risk factors are both genetic and environmental, your breast cancer risk can be minimized, but never completely eliminated.

Breast Cancer Risk Factors

Several risk factors are associated with breast cancer, including:

  • Age: Although a person can develop breast cancer at any age, a woman’s risk of developing breast cancer increases as she ages. For example, between the ages of 20 and 24 a woman has a one in 71,500 chance of developing breast cancer. Between the ages of 75 and 79, a woman’s chances increase to one in 220, according to the American Cancer Society (2010).
  • Diet: Women who are overweight or obese are at a greater risk of developing breast cancer than women of a healthy weight. Reducing your daily calories from fat to less than 20 or 30 percent can help cut your risk of developing breast cancer. Also, excessive alcohol consumption can increase a woman’s chance of developing the disease.
  • Family history: A woman whose mother, sister or grandmother currently has or has had breast cancer is two to three times more likely to develop breast cancer, according to the American Cancer Society (2010). BRCA, also known as the “breast cancer gene,” actually has two main variants that predispose a woman to familial breast cancer: BRCA1 and BRCA2.
  • Gender: Women are much more likely than men to develop breast cancer.
  • Hormones: Researchers believe that the greater a woman’s exposure to estrogen, the higher her risk of breast cancer. Thus, women are at a greater risk for developing breast cancer if they begin menstruating before age 11, have menstrual cycles that are shorter or longer than the average 26 to 29 days, have their first child after the age of 30 or stop menstruating after age 55.
  • Lifestyle: Countless studies have shown that women who exercise on a regular basis are less likely to develop cancer.
  • Medical history: A woman who has had breast cancer is at a greater risk of developing the disease again.
  • Race: In the United States, Caucasian women are slightly more likely than African American women to develop breast cancer. Both groups have a higher risk than all others.
  • Radiation therapy: Women who receive heavy doses of radiation therapy are at a higher risk of developing breast cancer, though only after a long delay.

Unfounded Breast Cancer Causes

The following have been debated as increasing breast cancer risk, but have no proven link to breast cancer:

  • Abortions: No credible evidence exists showing that having an abortion increases your risk of developing breast cancer.
  • Birth control pills: Studies have not shown a definite link between oral contraceptives and breast cancer.
  • Fibrocystic Breasts: Fibrocystic breasts have lumpy, dense tissue and are often associated with breast pain, especially right before a woman gets her period. Having fibrocystic breasts does not place a woman at greater risk for developing breast cancer.


National Cancer Institute. Abortion, miscarriage, and breast cancer risk. Retrieved October 12, 2010, from

The American Cancer Society (2010). Breast cancer facts and figures 2009-2010. Retrieved October 11, 2010, from