More than 2.9 million U.S. women with a history of the disease are alive today, mainly because of early detection. The five-year survival rate is close to 100 percent if the cancer is detected before it spreads.

Breast cancer is more common in women over 55 years old. Women of any age can develop this disease, however.

About 80 percent of breast lumps are not cancer.

Using deodorant can make the X-ray hard to read. You also should not use any lotions or powders under your arms or on your breasts that day.

The American Cancer Society (ACS) says the use of alcohol slightly increases the risk of getting breast cancer. One drink a day may cause a small increased risk; two to five drinks a day increases the risk to about 1½ times the risk of women who drink no alcohol.

The U.S. Preventive Services Task Force (USPSTF) does not recommend breast self-exams (BSEs) because evidence suggests BSEs do not lower risk for death from breast cancer. The ACS says BSEs are an option for women 20 and older as a means of familiarizing themselves with their breasts so they can notice changes more easily. Talking with your health care provider about the benefits and limitations can help you decide if you should start performing BSEs. If you choose to do a BSE, the best time is one week after your period starts. Check your breasts on the first day of each month if you have gone through menopause.

The risk for breast cancer increases somewhat for women who have children later in life or who have never had children.

The ACS says although no direct link between smoking and breast cancer has been discovered, some studies suggest it might increase breast cancer risk. This is particularly true for women who start smoking as teens.

Often, more than one type of treatment is needed.

Mammography is an important tool for detecting breast cancer early, when it’s easiest to treat. But the benefits and limitations of mammography vary based on factors like age and personal risk. Experts have different recommendations for mammography. Currently, the USPSTF recommends screening every two years for women ages 50 to 74. The ACS recommends yearly screening for all women ages 40 and older. Women should talk with their health care provider about their personal risk factors before making a decision about when to start getting mammograms or how often they should get them.

The ACS says women who have a mother, sister, or daughter with breast cancer have about double the risk. Women whose close blood relatives from either the mother’s or father’s side of the family had breast cancer also have an increased risk for the disease.

In 2005, the ACS said that long-term use of hormone therapy (HT) may slightly increase the risk for breast cancer. HT may also increase the risk for heart disease, blood clots, and strokes. Breast cancer in women who use HT for a prolonged time is often found at a more advanced stage, the ACS said. This may be because HT makes it more difficult to find breast cancer on a mammogram. The risk for breast cancer drops back to normal five years after a woman stops HT. Taking estrogen alone does not seem to increase the risk for breast cancer as much, if at all, according to the ACS. If HT is needed, it's best to use it at the lowest dose needed to control symptoms and for as short a time as possible.

Studies show that exercise reduces the risk, but how much exercise is not known. One study found that 75 minutes to 2-1/2 hours per week of brisk walking reduced the risk by 18 percent.

Heart disease is the leading cause.