Risk Factors for Breast Cancer

The two most significant risk factors for developing breast cancer are being female and increasing age. For example, a young woman in her 30s has a one in 233 chance (less than half a percent) of developing breast cancer, while the risk for a woman in her 60s is one in 27 (3.7 percent). The statistic that one in eight women is at risk for developing breast cancer is true only when considering the yearly risks for women of all ages—including those in their 90s.

  • Being female is the most important risk factor for breast cancer. Although men can get breast cancer, it is about 100 times more common in women.
  • Being older because most breast cancers occur after the age of 50.
  • Family history of breast, ovarian or prostate cancer may cause you to be two to three times more likely to develop breast cancer.
  • Inherited gene mutations have been linked to breast cancer. These include mutations in the following genes:
    • BRCA1
    • BRCA2
    • p53
    • CHEK2
    • ATM
    • PALB2

Other genes are under study and may also play a role in breast cancer.

  • Ashkenazi Jewish heritage poses a slightly higher risk of breast cancer than other women. This increased risk is likely due to the high incidence of BRCA1 and BRCA2 gene mutations in Jewish women of Eastern European descent (Ashkenazi Jews).
  • Radiation exposure to the chest area in adolescence or early adulthood (before age 30) increases the risk of breast cancer. This includes radiation treatment to the chest area for childhood cancer, treatment of other cancers such as lymphoma, as well as radiation to treat acne or enlarged thymus glands.
    • The amount of radiation from a mammogram is very small and does not increase your risk of getting breast cancer.
    • Very low doses of radiation (such as from X-rays and other medical imaging), when used appropriately, do not impact breast cancer risk.
  • Age at first period or at menopause is important because if you began having menstrual periods before age 12 or went through menopause after age 50, your risk for breast cancer is slightly higher than that of the average woman. It is thought that this is due to the amount of the female hormone estrogen to which your breasts have been exposed over your lifetime.
  • Age at first pregnancy (after age 30) or never having children puts you at a slightly higher risk. This may be due to the protective changes in breast tissue that occur with full-term pregnancies.
  • Hormone replacement therapy after the beginning of menopause slightly raises your risk of breast cancer. This added risk disappears about three to five years after you stop taking the hormones. The risk is greatest for combination hormone replacement therapy, which uses both estrogen and progestin, as opposed to therapy using estrogen alone.
  • Atypical hyperplasia refers to extra cells that grow in an abnormal pattern in the ducts (atypical ductal hyperplasia) or lobules (atypical lobular hyperplasia). Both are linked to an increased risk for developing breast cancer. If atypical hyperplasia is identified in a biopsy, surgery may be recommended.
  • Lobular carcinoma in situ (LCIS) is characterized by an increase in the number of cells confined inside breast lobules, the milk-producing glands. LCIS is not breast cancer but does increase risk and necessitates regular screening.
  • Women with extremely dense breasts on mammograms are four to five times more likely to get breast cancer than women with fatty breasts on mammograms.
  • Being overweight or obese increases your risk of breast cancer. It also increases the possibility that breast cancer will return after treatment, particularly after menopause.
  • Alcohol consumption. Women who have two to three alcoholic drinks per day have a higher risk of breast cancer than non-drinkers.

If you are interested in learning about your risk for developing breast cancer, our Breast Cancer Personalized Risk Assessment, Education and Prevention (B-PREP) Program offers an in-depth risk survey along with screening, genetic counseling, and education about prevention strategies.

Make an Appointment

If you are concerned that you are at-risk for breast cancer and would like an in-depth evaluation by our breast cancer specialists in the B-PREP Program, call (617) 732-8111. For more information on patient registration or scheduling an appointment with a Breast Specialist please visit our appointment page.


Read more about risk factors and risk reduction for breast cancer at Susan G. Komen.

Learn more about risk factors and risk reduction for breast cancer through information provided by The American Society of Breast Surgeons Foundation.

Visit the Kessler Health Education Library in the Bretholtz Center for Patients and Families to access computers and knowledgeable staff.

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