Risk Factors for Breast Cancer

This is the third article in the Understanding Breast Cancer Guide. This guide was developed by the HealthTree Education Team and was last updated and reviewed on May 18, 2026. 

Anything that increases your chance of developing cancer is called a risk factor. Sometimes, risk factors can directly cause cancer. Most often, though, risk factors do not directly cause cancer. Instead, many small changes over time lead to the genetic changes that cause cancer.

It is important to remember that having one or more risk factors for breast cancer does not guarantee you will develop breast cancer. It is also possible to develop breast cancer even if you do not have any known risk factors. Researchers are still learning how breast cancer develops.

What raises your risk for developing breast cancer?

• Sex. Breast cancer is about 100 times more common in women than in men, largely due to differences in estrogen and progesterone levels.
• Age. The risk of breast cancer increases with age. Most breast cancers are diagnosed in women over 50, though breast cancer can occur at any age.
• Personal history of breast cancer or certain breast conditions. Having had breast cancer in one breast increases the risk of developing it in the other. Certain non-cancerous breast conditions, such as atypical ductal hyperplasia, also raise risk.
• Family history. Having a first-degree relative (parent, sibling, or child) who had breast cancer raises your risk, especially if they were diagnosed at a young age or if multiple relatives are affected.
• Hereditary gene mutations. Certain inherited gene mutations significantly increase breast cancer risk:
  • BRCA1 and BRCA2 mutations are the most well-known hereditary breast cancer genes. They are also linked to ovarian, prostate, and pancreatic cancer risk.
  • PALB2, CHEK2, ATM, and other gene mutations are associated with moderate to high breast cancer risk.
• Dense breast tissue. Some women have dense breasts. They have more glandular and fibrous tissue than fatty tissue. They have a higher risk of breast cancer and may be harder to screen with standard mammography.
• Hormone exposure. Longer exposure to estrogen and progesterone increases breast cancer risk:
  • Starting menstruation before age 12 or entering menopause after age 55.
  • Having a first pregnancy after age 30, or never having been pregnant.
  • Using hormone replacement therapy (HRT) after menopause, particularly combined estrogen-progesterone therapy.
• Radiation exposure. Having had radiation therapy to the chest, particularly during childhood or adolescence, increases breast cancer risk later in life.
• Race and ethnicity. White women are slightly more likely to develop breast cancer overall, but Black women are more likely to be diagnosed at a younger age and at a later stage, and are more likely to have triple-negative breast cancer. Ashkenazi Jewish women have a higher likelihood of carrying BRCA1 or BRCA2 mutations.
• Obesity. Being overweight or obese, especially after menopause, increases breast cancer risk. Fatty tissue produces estrogen, and higher estrogen levels after menopause are associated with higher breast cancer risk.
• Alcohol use. Drinking alcohol regularly, even in moderate amounts, has been linked to an increased risk of breast cancer. Your risk increases with the amount consumed.
• Physical inactivity. Being physically inactive is associated with a higher risk of breast cancer.