Breast cancer refers to cancer that starts in any tissue that makes up the breast. The most common site for breast cancer to develop in women is in the ducts, which carry milk. Breast cancer can also develop in the lobules which is the site where milk is produced in women. The breast is also made up of fat and connective tissue, lymph nodes, and blood vessels.
While men have some breast tissue, they have few to no lobules and much lower levels of hormones so their breast duct cells are less developed. This means they have a lower chance to develop breast cancer. When it does occur, it is commonly referred to as “male breast cancer.”
How Common Is Breast Cancer?1
14% of new cancers
Breast cancer makes up 14% of all new cancers diagnosed each year. It is the second most common cancer among women in the US, after skin cancer.
1 in 8 women
Approximately 1 in 8 women (12.5%) will develop breast cancer in their lifetime.
1 in 1,000 men
While breast cancer can also develop in men, the chances that a man will develop this cancer in his lifetime is approximately 1 in 1,000 (~0.1%).
How Genetic Mutations Increase Breast Cancer Risk
Women and breast cancer risk
Risk among US women to develop breast cancer.
Men and male breast cancer risk
Risk among US men to develop male breast cancer.
People of certain ethnicities have a higher chance to develop breast cancer.
In general, Caucasian women have a higher risk of developing breast cancer than African American, Hispanic, and Asian women. However, African American women develop breast cancers that tend to be more aggressive. Researchers are still investigating why this is the case.
Having a family history of breast cancer increases risk.
Especially if the breast cancer in the family was diagnosed at a young age (before menopause), or in a first-degree relative (parent, sibling or child).
Environmental and lifestyle factors impact risk.
Exposure to certain substances, such as excessive amounts of alcohol, and hormone therapy with combined estrogen and progesterone for more than five years, are known to slightly increase the risk of breast cancer.
There are factors that can decrease risk.
Many factors can decrease the risk of breast cancer, such as high activity levels, lower body mass index (BMI), giving birth for the first time at an early age, and breastfeeding.
- SEER Cancer Statistics Factsheets: Female Breast Cancer. Surveillance, Epidemiology, and End Results (SEER) Program, National Cancer Institute Website. Accessed April 7, 2015. Available at seer.cancer.gov.
- What are the risk factors for breast cancer?. American Cancer Society Website. Updated February 22, 2016. Available at www.cancer.org.