Breast cancer is a malignant tumor that starts from cells of the breast. It forms in the breast tissues, usually in the ducts (tubes that carry milk to the nipple) and lobules (glands that make milk). This cancer can occur in both men and women, although male breast cancer is rare. Breast cancer is the most frequently diagnosed cancer in women, and any woman can develop it. However, several risk factors may increase the likelihood. Risk factors that can't be changed include: Race/ethnicity: Caucasian women develop breast cancer slightly more often than African-American women. However, African-American women tend to die of breast cancer more often. This may be partly because they often develop a more aggressive type of tumor. Aging: Two out of three women with invasive cancer are diagnosed after age 55. Personal history of breast cancer Previous breast irradiation Family history and genetic factors: Having a close relative, such as a mother or sister, with breast cancer increases the risk. Benign breast disease Dense breast tissue Diethylstilbestrol (DES) exposure Previous breast biopsy in which the tissue showed atypical hyperplasia Menstrual periods that began before age 12 Menopause that began after age 55 The most frequently cited lifestyle-related risk factors include: Not having children or having your first child after age 30 Oral contraceptive use Physical inactivity Alcohol use Long-term, postmenopausal use of combined estrogen and progestin Weight gain and obesity after menopause How is breast cancer diagnosed? First of all, it's important to remember that a lump or other changes in the breast, or an abnormal area on a mammogram, may not be a sign of cancer. To determine the cause of any symptoms, your doctor will perform a careful physical exam that includes taking your personal and family medical history. The exam may include palpation, or feeling the lump and the tissue around it—its size, its texture, and whether it moves easily. Fluid may be collected from spontaneous nipple discharge and sent to a lab to look for cancer cells. Most nipple secretions are not cancer; they may be caused by an injury, infection, or benign tumor. For women at high risk for breast cancer, a diagnostic procedure called ductal lavage may be used. Cells are collected from inside the milk ductal system, the location where most breast cancers begin. In addition to a physical exam, an imaging test will be performed, including one or more of the following: Diagnostic mammography: An X-ray used to diagnose unusual breast changes. Digital mammography: Images are electronically captured and stored on a computer rather than X-ray film. The images can be manipulated to help visualization. Ultrasound: Uses high-frequency sound waves that produce a picture called a sonogram. Magnetic resonance imaging: Uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images. Based on the results, your doctor may decide that no further tests are needed and no treatment is necessary. In such cases, he or she may want to check you regularly to watch for any changes. Often, however, the doctor must remove fluid or tissue from the breast to be sent to a lab to look for cancer cells. This procedure, called a biopsy, may be performed using a needle to take a small tissue sample or by a surgical method. There are several types of breast biopsy procedures; the type performed depends on the location and size of the breast abnormality. A biopsy is the only way to know for sure whether a breast abnormality is cancerous or not. Treatment for breast cancer can include surgery, radiation, chemotherapy, or hormone therapy. The good news is that breast cancer death rates have steadily declined. This is likely the result of earlier detection and better treatment.