Risk Factors Overview

Unfortunately, the exact causes of breast cancer are not known, although providers do know that trauma to the breast, such as bumping, bruising, or touching the breast does not cause cancer.
Research has shown that women with certain risk factors are more likely than others to develop breast cancer. A risk factor is something that increases the chance of developing a disease. The risk factors for breast cancer include:
  • Age
    The chance of developing breast cancer increases as a woman ages. Most cases of breast cancer occur in women over 60. Breast cancer is not common before menopause. One exception is that LCIS is more common in premenopausal women.
  • Personal History of Breast Cancer
    A woman who had breast cancer in one breast has an increased risk of getting cancer in the other breast.
  • Family History
    A woman's risk of breast cancer is higher if her mother, sister, or daughter has had breast cancer, especially if that breast cancer occurred before age 40. Having other relatives with breast cancer, in her mother’s or father’s family, may also increase a woman's risk.
  • Genetic Changes
    Some women are born with changes in certain genes that increase the risk of developing breast cancer. These genes include BRCA1, BRCA2, and several others. Genetic tests may show the presence of specific gene changes in families with an unusual number of women who have had breast cancer. Some families may have changes in their genes that are not detectable with currently available tests.
  • Reproductive and Menstrual History
    The older a woman is when she has her first child, the greater her chance of developing breast cancer. Also, women who had their first menstrual period before age 12 are at an increased risk of breast cancer as are women who went through menopause after age 55. Women who have never had children are also at an increased risk of breast cancer.
  • Hormone Therapy
    Women who take menopausal hormone therapy with estrogen plus progestin after menopause may have an increased risk of breast cancer.
  • Race
    Breast cancer is diagnosed more often in Caucasian women than Latino, Asian, or African American women.
  • Radiation Therapy to the Chest
    Women who had radiation therapy to the chest before age 30 are at an increased risk of developing breast cancer. This includes women treated with radiation for Hodgkin's lymphoma. Studies show that the younger a woman was when she received radiation treatment, the higher her risk of breast cancer later in life.
  • Breast Density
    Breast tissue may be dense or fatty. Older women whose mammograms show more dense tissue have an increased risk for breast cancer.
  • Taking Diethylstilbestrol, or DES
    DES was given to some pregnant women in the United States between about 1940 and 1971. Women who were exposed to DES in the womb or women who took DES during pregnancy may have a slightly increased risk of breast cancer.
  • Being Overweight or Obese After Menopause
    The chance of getting breast cancer after menopause is higher in women who are overweight or obese.

  • Lack of Physical Activity
    Women who are physically inactive throughout life may have an increased risk of breast cancer. Being active may help reduce risk by preventing weight gain and obesity.
  • Drinking Alcohol
    Studies suggest that the more alcohol a woman drinks, the greater her risk of breast cancer.
Researchers are continuing to study the effects of diet, physical activity, and genetics on breast cancer risk, along with whether certain substances in the environment can increase the risk of breast cancer.