Breast Cancer

Risk Factors

Some women develop breast cancer and others do not, and the risk factors for the disease vary. Breast cancer may affect younger women, but three-fourths of all breast cancers occur in women between the ages of 45 to 85.

In Situ and Invasive Breast Cancer

Researchers often talk about breast cancer in two ways: in situ and invasive. In situ refers to cancer that has not spread beyond its site of origin. Invasive applies to cancer that has spread to the tissue around it.

This chart shows what the approximate chances are of a woman getting invasive breast cancer in her lifetime.

Ages Chances
30 to 40...     |    Chances are 1 out of 227
40 to 50...     |    Chances are 1 out of 68
50 to 60...     |    Chances are 1 out of 41
60 to 70...     |    Chances are 1 out of 27
70 to 80...     |    Chances are 1 out of 25

Risk Factors

Risk factors are conditions or agents that increase a person's chances of getting a disease. Here are the most common risk factors for breast cancer.

  • Older age. The risk of breast cancer in a 70 year old woman is about 10 times that of a 30 year old woman, but risk decreases after age 85.
  • Personal and family history. A personal history of breast cancer or breast cancer among one or more of your close relatives, such as a sister, mother, or daughter.
  • Estrogen levels in the body. High estrogen levels over a long time may increase the risk of breast cancer. Estrogen levels are highest during the years a woman is menstruating.
  • Never being pregnant or having your first child in your mid-30s or later.
  • Early menstruation. Having your first menstrual period before age 12.
  • Breast density. Women with very dense breasts have a higher risk of breast cancer than women with low or normal breast density.
  • Combination hormone replacement therapy/Hormone therapy. Estrogen, progestin, or both may be given to replace the estrogen no longer made by the ovaries in postmenopausal women or women who have had their ovaries removed. This is called hormone replacement therapy. (HRT) or hormone therapy (HT). Combination HRT/HT is estrogen combined with progestin. This type of HRT/HT can increase the risk of breast cancer.
  • Exposure to radiation. Radiation therapy to the chest for the treatment of cancer can increase the risk of breast cancer, starting 10 years after treatment. Radiation therapy to treat cancer in one breast does not appear to increase the risk of cancer in the other breast.
  • Obesity. Obesity increases the risk of breast cancer, especially in postmenopausal women who have not used hormone replacement therapy.
  • Alcohol. Drinking alcohol increases the risk of breast cancer. The level of risk rises as the amount of alcohol consumed rises.
  • Gaining weight after menopause, especially after natural menopause and/or after age 60.
  • Race. White women are at greater risk than black women. However, black women diagnosed with breast cancer are more likely to die of the disease.
  • Inherited gene changes. Women who have inherited certain changes in the genes named BRCA1 and BRCA2 have a higher risk of breast cancer, ovarian cancer and maybe colon cancer. The risk of breast cancer caused by inherited gene changes depends on the type of gene mutation, family history of cancer, and other factors. Men who have inherited certain changes in the BRCA2 gene have a higher risk of breast, prostate and pancreatic cancers, and lymphoma.

Get information about the BRCA1 and BRCA2 genetic mutations and testing for them.

Five percent to 10 percent of all breast cancers are thought to be inherited.

(Watch the video to learn more about a family that carries a gene which places them at high risk for breast cancer. To enlarge the video, click the brackets in the lower right-hand corner. To reduce the video, press the Escape (Esc) button on your keyboard.)

Warning Signs

When breast cancer first develops, there may be no symptoms at all. But as the cancer grows, it can cause changes that women should watch for. You can help safeguard your health by learning the following warning signs of breast cancer.

  • a lump or thickening in or near the breast or in the underarm area
  • a change in the size or shape of the breast
  • nipple discharge or tenderness, or the nipple is pulled back or inverted into the breast
  • ridges or pitting of the breast. The skin looks like the skin of an orange
  • a change in the way the skin of the breast, areola, or nipple looks or feels. For example, the skin may be warm, swollen, red, or scaly.

Don't Ignore Symptoms

You should see your doctor about any symptoms like these. Most often, they are not cancer, but it's important to check with the doctor so that any problems can be diagnosed and treated as early as possible.

Some women believe that as they age, health problems are due to "growing older." Because of this myth, many illnesses go undiagnosed and untreated. Don't ignore your symptoms because you think they are not important or because you believe they are normal for your age. Talk to your doctor.