Risk Factors for Breast Cancer

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 healthcare provider 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. However, men can develop breast cancer as well; it is estimated that approximately 2,100 men will develop breast cancer in the United States in 2007. And although there is great emphasis on risk factors for developing breast cancer, a great many cases occur in patients with no known risk factors. Having breasts makes you at risk for having breast cancer.

Genetic 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 mutation in the BRCA1 or BRCA2 breast cancer genes increases your risk.


Breast cancer can develop at any age in adulthood. However, it is quite rare in women under age 35. The chance of developing breast cancer increases with age, and three out of four cases occur in women over age 50. However, it is never safe to say that “you are too young to get breast cancer.”

Medical Condition

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 (that is, dense breasts)
  • Previous breast exposure to radiation therapy before age 30
  • Pregnancy after age 30, or no pregnancy at all
  • Overweight, particularly after menopause
  • Increased exposure to estrogen, which includes:
    • First menstrual period before age 13
    • Menopause after age 51
    • Prolonged use of estrogen replacement therapy, especially unopposed by progesterone
  • Exposure to large amounts of radiation (x-rays or cancer treatment), such as scoliosis treatment or treatment for Hodgkin’s disease
  • Previous biopsy results that indicate atypical hyperplasia or radial scar formation

Specific Lifestyle Factors

Lifestyle factors that increase breast cancer risk include:

  • Drinking three or more alcoholic drinks daily
  • Sedentary lifestyle
  • Smoking

Ethnic Background

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


National Breast and Cervical Cancer Early Detection Program, Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/cancer/nbccedp/. Accessed January 31, 2006.

National Cancer Institute website. Available at: http://www.cancer.gov. Accessed January 31, 2006.

National Center for Women’s Health website. Available at: http://www.4woman.gov/. Accessed January 31, 2006.

Last reviewed April 2007 by Jondavid Pollock, MD, PhD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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