Cancer Breast Cancer Causes & Risk Factors Breast Cancer Guide Breast Cancer Guide Symptoms Causes Diagnosis Treatment Coping Prevention Causes and Risk Factors of Breast Cancer By Lisa Fayed Lisa Fayed is a freelance medical writer, cancer educator and patient advocate. Learn about our editorial process Lisa Fayed Medically reviewed by Medically reviewed by Doru Paul, MD on November 18, 2019 Doru Paul, MD, is triple board-certified in medical oncology, hematology, and internal medicine. He is an associate professor of clinical medicine at Weill Cornell Medical College and attending physician in the Department of Hematology Oncology at the New York Presbyterian Weill Cornell Medical Center. Learn about our Medical Review Board Doru Paul, MD Updated on January 27, 2020 Print Table of Contents View All Common Risk Factors Heredity and Genetics Lifestyle Risk Factors Next in Breast Cancer Guide How Breast Cancer Is Diagnosed Breast cancer is influenced by heredity, but it can develop even if you don't have a family history or carry genes for the disease. There are a number of conditions and environmental exposures associated with alterations in the breast tissue that lead to breast cancer, including smoking, hormone therapy, having dense breasts, and being overweight. Breast cancer affects one in every eight women throughout their lifetimes. While it is rare, men can develop breast cancer as well. Whether you have a family history of breast cancer or not, attention to the causative factors may help prevent you from developing the disease. Verywell / Nusha Ashjaee Common Risk Factors Breast cancer occurs when there are slight changes in the cells and tissues of the breast. These altered cells cause the formation of a tumor (or more than one tumor). These tumors can be aggressive, invading normal breast tissue, and potentially even spreading to other parts of the body (including the bones, lungs, and brain) through the lymph nodes and bloodstream. While the cause or causes of these cellular changes has only been hypothesized thus far, there are a number of factors associated with breast cancer. These risk factors increase the chance of developing the disease, and they may do so by causing the condition or by reducing the body's protection against it. Age It is estimated that 80 percent of women diagnosed with breast cancer are 50 or older. Most types of cancer, including breast cancer, occur more frequently with advancing age. This is due to the build-up of risk factors, age-related changes in the cells of the body, and declining immune system protection from cancer. Age of First Menses and Menopause Having your first menstrual period at an earlier age and experiencing menopause at a later age—meaning more years of having your period—is associated with a higher chance of developing breast cancer. This is believed to be due to the hormonal changes that occur each month with a woman's menstrual cycle. Dense Breasts You can't control whether you have dense breasts or not, and this characteristic is linked with an increased chance of developing breast cancer. Some efforts are underway to standardize mammogram reports of dense breasts and their associated breast cancer risks. A Screening Strategy for Women With Dense Breasts Hormone Therapy Oral contraceptives and hormone replacement therapy contain estrogen and progesterone. These hormones have been linked with breast cancer, but they do not necessarily pose this risk for all women. Your medical history and family history play a role in whether any type of hormone could increase your risk of developing breast cancer. Previous Cancer Women (and men) who have previously been diagnosed and treated for any type of cancer, especially breast or ovarian cancer, are at a greater risk of developing breast cancer. Will My Breast Cancer Return? Pregnancy and Breastfeeding Women who never become pregnant or who have children at a later age are more likely to develop breast cancer. Breastfeeding is also associated with a lower risk of the disease. These factors are believed to be related to the protective effects of hormonal changes that occur during pregnancy and lactation. Heredity and Genetics Having a mother, sister, or daughter with breast cancer doubles your chances of getting the disease yourself. About 5 percent to 10 percent of women with breast cancer have a family history of the condition. That said, hereditary breast cancer is complicated. Many breast cancer genes have been identified, but not all women with breast cancer have these genes, even when breast cancer runs in the family. And many women who have the genes do not have a family history of breast cancer. How Family History Affects Your Breast Cancer Risk Breast Cancer Genes The most common genetic mutation is that of the BRCA gene pair, referred to as BRCA1 and BRCA2, but there are a number of breast cancer genes, which are often referred to as non-BRCA breast cancer genes. There are also probably additional breast cancer genes that have not yet been identified. Because there are so many breast cancer genes, they are unlikely to cause breast cancer in the same way. Having a breast cancer gene could predispose you to the condition. When a genetic predisposition is combined with other risk factors, it becomes even more likely that you will develop the disease. If you have breast cancer in your family, your doctor might recommend that you have genetic testing. Lifestyle Risk Factors There are a few activities and exposures that are linked with breast cancer. While they are often described as lifestyle choices, some of these behaviors are in fact addictive, making them difficult to stop. If you drink, smoke, or consume an unhealthy diet, consider getting professional help if you want to change your habits. Lifestyle risk factors associated with breast cancer include: Smoking: Cigarettes contain a number of chemicals, many of which are known carcinogens. Smoking is associated with breast cancer, as well as a number of other types of cancer.Alcohol consumption: Women who drink two to five drinks a day have 1.5 times the risk of getting breast cancer compared to women who do not drink alcohol.Weight: Obesity may increase the risk of breast cancer. This is largely due to altered estrogen hormone levels that are associated with weight gain in women.Diet: There have been a number of theories about food and breast cancer. Experts suggest that some food preservatives and dyes may be carcinogenic and can increase the risk of all cancers, including breast cancer. Read more about Angiosarcoma of the breast. About Soy There have been many controversies regarding soy and breast cancer. Soy, which is present in a small number of foods—including meat substitutes, tofu, edamame, and miso—has been considered both a cause and a preventative strategy of breast cancer. Experts still aren't in agreement about the impact of soy on breast cancer, so it is best to check with your doctor, especially if you have had breast cancer or are at risk of the disease. How Breast Cancer Is Diagnosed Was this page helpful? Thanks for your feedback! Get honest information, the latest research, and support for you or a loved one with breast cancer right to your inbox. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Terry MB, Michels KB, Brody JG, et al. Environmental exposures during windows of susceptibility for breast cancer: a framework for prevention research. Breast Cancer Res. 2019;21(1):96. doi:10.1186/s13058-019-1168-2 Howlader N, Noone AM, Krapcho M, et al. (eds). SEER cancer statistics review, 1975-2016, National Cancer Institute. Bethesda, MD, based on November 2018 SEER data submission, posted to the SEER web site, April 2019. Akram M, Iqbal M, Daniyal M, Khan AU. Awareness and current knowledge of breast cancer. Biological Research. 2017;50(1):14-17. doi:10.1186/s40659-017-0140-9 American Cancer Society. Breast cancer facts & figures 2019-2020. Cancer.org. Published 2019. Collaborative Group on Hormonal Factors in Breast Cancer. Menarche, menopause, and breast cancer risk: individual participant meta-analysis, including 118,964 women with breast cancer from 117 epidemiological studies. Lancet Oncol. 2012;13(11):1141-51. doi:10.1016/S1470-2045(12)70425-4 Fisher V. Exploring the relationship between mammographic breast density and breast cancer. National Cancer Institute. Published 2017. American Cancer Society medical and editorial content team. Menopausal hormone therapy and cancer risk. Cancer.org. Published 2015. American Cancer Society medical and editorial content team. How does radiation therapy affect the risk of second cancers? Cancer.org. Published 2014. National Cancer Institute. Reproductive history and cancer risk. National Cancer Institute. Published 2016. Victora CG, Bahl R, Barros AJ, et al. Breastfeeding in the 21st century: epidemiology, mechanisms, and lifelong effect. Lancet. 2016;387(10017):475-90. doi:10.1016/S0140-6736(15)01024-7 American Cancer Society medical and editorial content team. Breast cancer risk factors you cannot change. Cancer.org. Published 2019. Shiyanbola OO, Arao RF, Miglioretti DL, et al. Emerging trends in family history of breast cancer and associated risk. Cancer Epidemiol Biomarkers Prev. 2017;26(12):1753-1760. doi:10.1158/1055-9965.EPI-17-0531 Baxter JS, Leavy OC, Dryden NH, et al. Capture Hi-C identifies putative target genes at 33 breast cancer risk loci. Nat Commun. 2018;9(1):1028. doi:10.1038/s41467-018-03411-9 Kispert S, McHowat J. Recent insights into cigarette smoking as a lifestyle risk factor for breast cancer. Breast Cancer (Dove Med Press). 2017;9:127–132. Published 2017 Mar 7. doi:10.2147/BCTT.S129746 Division of Cancer Prevention and Control, Centers for Disease Control and Prevention. What are the risk factors for breast cancer? Published 2018. Rosendahl A, Bergqvist M, Lettiero B, Kimbung S, Borgquist S. Adipocytes and obesity-related conditions jointly promote breast cancer cell growth and motility: associations with CAP1 for prognosis. Front Endocrinol (Lausanne). 2018;9. doi:10.3389/fendo.2018.00689 Fiolet T, Srour B, Sellem L, et al. Consumption of ultra-processed foods and cancer risk: results from NutriNet-Santé prospective cohort. BMJ. 2018;360(8141):k322. doi:10.1136/bmj.k322 Ziaei S, Halaby R. Dietary isoflavones and breast cancer risk. Medicines (Basel). 2017;4(2):18. doi:10.3390/medicines4020018