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 health care provider what you can do to reduce your risk.

Risk factors for breast cancer include the following:


Women are at much greater risk for breast cancer than men; breast cancer is the most common form of cancer in American women. However, men can develop breast cancer as well; it is estimated that approximately 1,000 men develop breast cancer each year in the U.S.

Genetic Factors

Women who have a family member who had breast cancer (mother, sister, or daughter who developed breast cancer at a young age) have a higher risk of developing breast cancer. However, a lack of family history does not protect you; most women who develop breast cancer have no family history of this disease. Women of Ashkenazi heritage are also at greater risk.

If you are of Ashkenazi heritage, or your family has a history of cancer, including breast and ovarian, your doctor may suggest genetic testing to determine if you have any abnormal mutations in the two types of genes associated with breast cancer: BRCA-1 and BRCA-2. There are other genetic syndromes that may be causes of familial breast cancer, such as those affecting the following genes:

  • The p53 gene
  • The AT gene
  • The genes that cause hereditary non-polyposis colon cancer (HNPCC)
  • The PTEN gene


The risk of breast cancer increases with age. However, it is quite rare in women under age 35. Most breast cancers occur in women over the age of 60. By age 50, the risk of developing breast cancer is approximately 1 in 50 women. If you live to an extreme older age, the risk of developing breast cancer is approximately 1 in 9.

Increased Exposure to Estrogen

High levels of estrogen have been linked to the development of breast cancer. Certain factors increase your exposure to estrogen, including the following:

  • First menstrual period before age 13
  • Menopause after age 51
  • Use of estrogen replacement therapy
  • First pregnancy after age 30 or no pregnancy at all

Specific Lifestyle Factors

Certain lifestyle factors have been found to increase the risk of breast cancer.

  • Excess weight – women who carry excess weight, especially after menopause, are at an increased risk of developing breast cancer.
  • Physical inactivity – exercise at any age has been shown to be beneficial in preventing breast cancer. Women who are sedentary after menopause are at greater risk of developing breast cancer.
  • Alcohol intake – some studies have shown that women who drink moderate amounts of alcohol each week are at greater risk for developing breast cancer.

Medical Conditions

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
  • Exposure to large amounts of radiation (x-rays or cancer treatment), such as for treatment of Hodgkin’s disease, especially during the teenage years
  • Previous biopsy results that indicate atypical hyperplasia or lobular carcinoma in situ
  • Breasts that are dense; breast cancer is more common in breasts that are dense than in breasts with a lot of fatty tissue
  • Breast exposure to radiation therapy before age 30
  • History of DES usage – DES (diethylstilbestrol) is a synthetic form of estrogen that was used between the early 1940s and 1971. It was given to pregnant women to prevent certain complications. Women who took DES during pregnancy are at a slightly higher risk for breast cancer. However, this does not appear to be the case for their daughters who were exposed to DES before birth.

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.