Breast Cancer Causes and Risk Factors
Learn about what causes breast cancer, common risk factors, and how to reduce your risk.
What causes breast cancer?
Breast cancer occurs when breast cells mutate and become cancerous cells. These cells then divide and multiply, turning into tumors. But in terms of what causes those changes to happen, experts aren't sure.
While there isn't a specific, single cause of breast cancer, there are several factors that can increase your risk of getting breast cancer.
Breast Cancer Risk Factors for Women
Here are some factors—both in and outside of your control—that can increase your chances of getting breast cancer.
Genetic Factors
These are factors that are passed down and cannot be changed. If you are at an increased risk due to personal and family history, your provider may recommend genetic testing and counseling. A genetic counselor will evaluate your risk on a personal basis.
Age
As you get older, you have a higher risk of getting breast cancer because you've been exposed to estrogen for longer.
Race and Ethnicity
Black women have a 5% lower incidence than White women but have a 38% higher rate of mortality.1
Type of Breast Tissue
Those with dense breast tissue are more likely to be diagnosed with breast cancer.
Certain Genetic Mutations
While BRCA1 and BRCA2 are the most common types of genetic mutations, there are several other types of genes linked to a higher risk of breast cancer.
Menstruation and Pregnancy History
The more periods you've had, the more estrogen you've been exposed to. Women who have had a baby before age 35 are at a lower risk.
Family History
You're at a higher risk if your parent or child has been diagnosed with breast or ovarian cancer. The risk increases if they were diagnosed before age 50.
Environmental and Lifestyle Factors
These are factors that likely can be changed.
Hormonal Birth Control and Other Pills
Some hormonal therapies, like certain birth control pills, can increase your risk for breast cancer.
Alcohol and Tobacco Use
Those who consume moderate to high levels of alcohol or smoke cigarettes are at a higher risk for breast cancer.
Weight
Being overweight or obese, especially after menopause, can increase your breast cancer risk. This is because fat cells make and store estrogen.
Sedentary Lifestyle
You're risk of breast cancer is higher if you are not as physically active.
Radiation Exposure
Individuals who had radiation treatments done (especially to their chest) are at a higher risk of developing breast cancer.
What are the breast cancer risk factors for men?
Men have a slightly different set of factors that can put them at a greater risk of developing breast cancer.
Older Age
On average, men who get diagnosed with breast cancer are around 70 years old.
Estrogen-related Medications
Some hormone therapy pills that contain estrogen can increase the chances of a man getting breast cancer.
Family History
If you've had a close family member who has or have had breast cancer, you're at a greater risk.
Gene Mutations
Similar to with women, men who've inherited certain gene mutations (like the BRCA1 and BRCA2 mutations) are at a higher risk.
Klinefelter Syndrome
Roughly 1 in 1,000 men are born with Klinefelter Syndrome, which can cause higher level of estrogens (female hormones).2
Overweight or Obese
As is the case with women, men who weigh more or are obese have a higher breast cancer risk.
How can I lower my risk of having breast cancer?
- Drink little to no alcohol
- Maintain a healthy weight
- Exercise regularly
- Limit the use of hormone therapy, if possible
Preventive Breast Cancer Surgery
Those who have a very high risk of getting breast cancer may choose to have preventive surgery. This is referred to as either a bilateral mastectomy or bilateral prophylactic mastectomy. In this procedure, both breasts are removed (which includes most, but not all, breast tissue) to prevent breast cancer.
The following women may be candidates a risk-reducing bilateral mastectomy:
- Carriers of certain gene mutations (such as BRCA1, BRCA2, PALB2, CDH1, PTEN, or TP53)
- Those who have had more than one relative diagnosed with breast cancer, especially prior to age 50.
After the surgery, many women choose to have breast reconstruction. Learn more about breast cancer treatment options. Talk with your health care provider if you have concerns about your breast cancer risk.
Better Early Breast Cancer Detection with the Know Your Lemons App
Are you confident about performing self-breast exams? The Know Your Lemons app can improve your chances of finding breast cancer early. Features include:
- Self-exam audio guide, video, and report
- Custom screening plan
- Period tracker
- Mammogram scheduler
AskEllyn.ai: A Companion for Your Breast Cancer Journey
Whether you were just diagnosed, are going through treatment, or have a loved one with breast cancer, you deserve support. AskEllyn.ai is a free AI companion, available 24/7. Ask questions or simply receive comfort in this private and unique chat experience.
1American Cancer Society, Breast Cancer Facts & Figures: 2024-2025, https://www.cancer.org/content/dam/cancer-org/research/cancer-facts-and-statistics/breast-cancer-facts-and-figures/2024/breast-cancer-facts-and-figures-2024.pdf, accessed March 26, 2025.
2 American Cancer Society, Risk Factors for Breast Cancer in Men, https://www.cancer.org/cancer/types/breast-cancer-in-men/causes-risks-prevention/risk-factors.html, accessed March 26, 2025.
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