Breast Cancer Risk Factors 

When you're told that you have breast cancer, it's natural to wonder what may have caused the disease. But no one knows the exact causes of breast cancer. There are certain risk factors that are more likely than others to develop breast cancer. Some of the more common risk factors include:

Age
The chance of getting breast cancer increases as you get older. Most women are over 60 years old when they are diagnosed.

Personal health history
Having breast cancer in one breast increases your risk of getting cancer in your other breast. Also, having certain types of abnormal breast cells (atypical hyperplasia, lobular carcinoma in situ [LCIS], or ductal carcinoma in situ [DCIS]) increases the risk of invasive breast cancer. These conditions are found with a breast biopsy.

Family health history
Your risk of breast cancer is higher if your mother, father, sister, or daughter had breast cancer. The risk is even higher if your family member had breast cancer before age 50. Having other relatives (in either your mother's or father's family) with breast cancer or ovarian cancer may also increase your risk.

Reproductive and menstrual history
The older a woman is when she has her first child, the greater her chance of breast cancer. Also at an increased risk are women who never had children, women who had their first menstrual period before age 12, women who went through menopause after age 55, and women who have taken menopausal hormone therapy for many years.

Race
In the United States, breast cancer is diagnosed more often in white women than in African American/black, Hispanic/Latina, Asian/Pacific Islander, or American Indian/Alaska Native women.

Breast density
Breasts appear on a mammogram (breast x-ray) as having areas of dense and fatty (not dense) tissue. Women whose mammograms show a larger area of dense tissue than the mammograms of women of the same age are at increased risk of
breast cancer.

Being overweight or obese after menopause
The chance of getting breast cancer after menopause is higher in women who are overweight or obese.

Lack of physical activity
Women who are physically inactive throughout life may have an increased risk of breast cancer.

Drinking alcohol
Studies suggest that the more alcohol a woman drinks, the greater her risk of breast cancer.

Having a risk factor does not mean that a woman will get breast cancer. Most women who have risk factors never develop breast cancer.

 Learn more about breast cancer risk factors and prevention from the National Cancer Institute.