A risk factor is anything that increases your risk for developing a disease. As medical researchers discover more about the causes of breast cancer, the list of risk factors may change over time.

Having even several of these risk factors doesn't mean you'll get breast cancer. There are different types of risk factors. Some you can't do anything about such as your age, genes and gender. Others like drinking alcohol and watching your weight are risk factors over which you have some measure of control.

If you have concerns about your own risk factors, discuss them with your physician.

Your gender
Men can develop breast cancer, but it is about 100 times more common among women. Women are at higher risk because their breast cells are constantly exposed to female hormones, which promote cell growth.

Your age
Your risk of developing breast cancer increases as you get older. About one out of eight invasive breast cancers are found in women younger than 45, while about two out of three invasive breast cancers are found in women age 55 or older.

Your genes
It is believed that about 5 to 10 percent of breast cancer cases are the result of gene defects inherited from a parent. The most common cause of hereditary breast cancer is an inherited mutation in the BRCA1 and BRCA2 genes. Other gene mutations can also increase your risk of breast cancer, but they are much rarer and don't increase the risk as much as BRCA.

Your family history
Breast cancer risk is higher among women whose close blood relatives have breast cancer. Remember that more than 70 percent of women who get breast cancer do not have a family history of the disease.

Personal history of breast cancer
Once you have had breast cancer, you are at an increased risk of developing a new breast cancer.

White women are slightly more likely to develop breast cancer than are African-American women. African-American women tend to have more aggressive tumors and are more likely to die from breast cancer.

Dense breast tissue
Women with denser breast tissue (as seen on a mammogram) have more glandular tissue and less fatty tissue, and have a higher risk of breast cancer.

Certain precancerous breast conditions
Women diagnosed with certain benign breast conditions may have an increased risk of breast cancer. These changes are often discovered only after you have a breast biopsy for another reason, but they can double your risk of developing breast cancer. If you have carcinoma in situ, discuss treatment and monitoring options with your doctor.

Previous chest radiation
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. The younger you were when you received the treatments, the greater your risk.

Exposure to estrogen
Women who have had more menstrual cycles because they started menstruating before age 12 and/or went through menopause at or after age 55 have a slightly higher risk of breast cancer. The risk is also slightly higher for women who never had children, or whose first pregnancy occurred when they were age 35 or older. This may be related to a higher lifetime exposure to hormones.

Recent oral contraceptive use
Studies have found that women using oral contraceptives (birth control pills) have a slightly greater risk of breast cancer than women who have never used them. Women who stopped using oral contraceptives more than 10 years ago do not appear to have any increased breast cancer risk.

Post-menopausal hormone therapy
Studies have shown a slightly higher risk of breast cancer for women taking the particular combination of hormone therapy — estrogen plus progestin. Discuss the benefits and risks with your doctor.

Use of alcohol is clearly linked to an increased risk of developing breast cancer. The risk increases with the amount of alcohol consumed. The American Cancer Society recommends that women limit their consumption of alcohol to no more than one drink a day.

Being overweight or obese
Extra weight has been found to increase breast cancer risk, especially for women after menopause. The risk appears to be increased for women who gained weight as an adult but may not be increased among those who have been overweight since childhood.

Exposure to certain carcinogens
Chemicals found mainly in cigarette smoke and charred red meat have shown to increase your chances of developing breast cancer. Exposure to certain pesticides also may increase your risk, but more research needs to be done to establish a clear link.

Lack of physical activity
Evidence is growing that physical activity in the form of exercise reduces breast cancer risk. To reduce your risk of breast cancer, the American Cancer Society recommends 45 to 60 minutes of intentional physical activity five or more days a week.

Tobacco smoke and secondhand smoke
There appears to be a link between secondhand smoke and breast cancer among women with a family history of breast cancer.