Breast Cancer Risk Factors

One in eight women will develop breast cancer, but there are certain factors that may put you at a greater risk of developing breast cancer. These include:


The risk of developing breast cancer increases with age, with more than 75 percent of cases occurring in women over the age of 50.

Family History

With the exception of aging and being a woman, the single most important risk factor for developing breast cancer is having a family history of the disease. About 20 percent of women with breast cancer have one or two relatives with breast cancer.

The risk is greater if a relative’s cancer developed before menopause or if the disease was found in both breasts. Having two first-degree relatives (a mother, sister or daughter) with breast cancer increases the risk five-fold. However, only the risk of cancer is increased. Most women who have cancer in their family will not develop cancer.

Women with a family history of the disease now have the option of pursuing genetic counseling and testing, which can provide direction about how to manage future risk, both for themselves and potentially for others in their family.


Women whose first menstrual period occurred before the age of 12 and those who reach menopause after the age of 55 are at greater risk because of a longer lifetime exposure to the female hormone estrogen. While estrogen has not been found to directly cause breast cancer, it has been found to cause breast cancer cells to grow.

Personal History of Breast Cancer

A woman who has had cancer in one breast is more likely to develop cancer in the other breast later.

History of Atypical Hyperplasia

Atypical hyperplasia is an overgrowth of atypical cells. This pre-malignant condition may require evaluation more frequently than annual screening mammography and breast examination. There may also be a role for medication to lower the risk of breast cancer.

Previous Breast Radiation

Women who have had radiation therapy of the chest as a child or young woman as treatment for another cancer such as Hodgkin’s disease or non-Hodgkin’s lymphoma are at significantly increased risk for breast cancer.


White women are slightly more likely to develop breast cancer than are African-American women. However, African Americans are more likely to die of this cancer. In general, Asian/Pacific Islander, Native American and Hispanic women have a relatively lower risk of developing breast cancer.

Socioeconomic Status

Women in higher income brackets in the United States develop breast cancer more often than women in lower income brackets. Women of low socio-economic status, however, are more likely to be diagnosed with late-stage disease and die of the disease.

Childbearing History

Women who have had no children or who had their first child after age 30 have a slightly higher breast cancer risk.

Hormone Replacement Therapy

Long-term use (several years or more) of hormone replacement therapy after menopause, particularly estrogen and progesterone in combination, increases the risk of breast cancer.