A risk factor is something that increases your likelihood of getting a disease or condition.

It is possible to develop breast cancer with or without the risk factors listed below. However, the more risk factors you have, the greater your likelihood of developing breast cancer. If you have a number of risk factors, ask your doctor what you can do to reduce your risk.

Breast cancer is found predominantly in women and is the most common form of cancer in American women. Breast cancer in men is rare.

Although there is great emphasis on risk factors for developing breast cancer, a great many cases occur in people with no known risk factors.

Women who have a family history of breast cancer (mother, sister, or daughter) have a higher risk factor of developing breast cancer. However, a lack of family history does not protect you from developing breast cancer; approximately 90%-95% of women who develop breast cancer have no family history of this disease.

Additionally, having a genetic abnormality increases your risk. This includes the BRCA1 and BRCA2 genes, as well as others. Rare genetic diseases can also increase risk.

The chance of developing breast cancer increases with age; three out of four cases occur in women over age 50. This occurs in men around age 60. Although breast cancer is more common as you age, breast cancer can occur at any age.

The following medical conditions have been found to increase the risk of developing breast cancer:

  • Prior personal history of breast cancer, or other abnormalities in the breast tissue
  • Breasts that have a high proportion of lobular and ductal tissue instead of fatty tissue, which makes the breast tissue more dense
  • Previous breast exposure to radiation therapy before age 30
  • Pregnancy after age 30, or no pregnancy at all
  • Absence of breast-feeding
  • Overweight, particularly after menopause
  • Increased exposure to estrogen, which includes:
    • First menstrual period before age 13
    • Menopause after age 51
    • Prolonged use of hormone replacement therapy
  • Previous biopsy results that indicate atypical hyperplasia, lobular carcinoma in situ, or radial scar formation

Lifestyle factors that increase breast cancer risk include:

  • Drinking three or more alcoholic drinks daily
  • Having a sedentary lifestyle
  • Smoking
  • Consuming a diet that is high in red meat

In the US, Caucasian, Hawaiian, and African American women have the highest rates of breast cancer. The lowest rates occur among Korean, American Indian, and Vietnamese women.

Revision Information

  • Breast cancer. National Cancer Institute website. Available at: http://www.cancer.gov/cancertopics/types/breast. Accessed January 9, 2014.

  • Breast cancer. Office on Women's Health website. Available at: http://www.womenshealth.gov/breast-cancer/index.html. Updated November 17, 2010. Accessed January 9, 2014.

  • National Breast and Cervical Cancer Early Detection Program. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/cancer/nbccedp. Updated December 13, 2013. Accessed January 9, 2014.

  • Risk factors for breast cancer. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated October 24, 2013. Accessed January 9, 2013.

  • 6/24/2014 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Farvid MS, Cho E, et al. Dietary protein sources in early adulthoood and breast cancer incidence: prospective cohort study. BMJ. 2014 Jun 10;348:g3437.