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. 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.  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. 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. 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. Never being pregnant or having your first child in your mid-30s or later. - Early menstruation. Having your first menstrual period before age 12. 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.  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.  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. 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.  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. 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. 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. 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. 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. Five percent to 10 percent of all breast cancers are thought to be inherited. Get information about the BRCA1 and BRCA2 genetic mutations and testing for them. 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  - a dimple or puckering in the skin of the breast  -  a nipple turned inward into the breast  -  fluid, other than breast milk, from the nipple, especially if it's bloody  - scaly, red, or swollen skin on the breast, nipple, or areola (the dark area of skin around the nipple)  - dimples in the breast that look like the skin of an orange. a lump or thickening in or near the breast or in the underarm area a change in the size or shape of the breast a dimple or puckering in the skin of the breast a nipple turned inward into the breast fluid, other than breast milk, from the nipple, especially if it's bloody scaly, red, or swollen skin on the breast, nipple, or areola (the dark area of skin around the nipple) dimples in the breast that look like the skin of an orange. 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.