Breast cancer

A risk factor is anything that makes it more likely you'll get a particular disease. But having one or even several risk factors doesn't necessarily mean you'll develop cancer — many women who develop breast cancer have no known risk factors other than simply being women.

Factors that are associated with an increased risk of breast cancer include:

• Being female. Women are much more likely than men are to develop breast cancer.
• Increasing age. Your risk of breast cancer increases as you age. Women older than 55 have a greater risk than do younger women.
• A personal history of breast cancer. If you've had breast cancer in one breast, you have an increased risk of developing cancer in the other breast.
• A family history of breast cancer. If you have a mother, sister or daughter with breast cancer, you have a greater chance of being diagnosed with breast cancer. Still, the majority of people diagnosed with breast cancer have no family history of the disease.
• Inherited genes that increase cancer risk. Certain gene mutations that increase the risk of breast cancer can be passed from parents to children. The most common gene mutations are referred to as BRCA1 and BRCA2. These genes can greatly increase your risk of breast cancer and other cancers, but they don't make cancer inevitable.
• Radiation exposure. If you received radiation treatments to your chest as a child or young adult, you're more likely to develop breast cancer later in life.
• Obesity. Being overweight or obese increases your risk of breast cancer because fat tissue produces estrogen that may help fuel certain cancers.
• Beginning your period at a younger age. Beginning your period before age 12 increases your risk of breast cancer.
• Beginning menopause at an older age. If you began menopause after age 55, you're more likely to develop breast cancer.
• Having your first child at an older age. Women who give birth to their first child after age 35 may have an increased risk of breast cancer.
• Postmenopausal hormone therapy. Women who take hormone therapy medications that combine estrogen and progesterone to treat the signs and symptoms of menopause have an increased risk of breast cancer.
• Drinking alcohol. Drinking alcohol increases the risk of breast cancer. Experts recommend no more than one alcoholic beverage a day for women.

Other risk factors that have been suggested, but don't play any role in the development of breast cancer include tightfitting bras, antiperspirants, breast implants and shift work.