Breast cancer is a malignant tumor that develops from cells of the breast. Although men occasionally get the disease, it is considered a "women's cancer."
Many women develop breast lumps, and most are benign (not cancerous). In these cases, the lump is usually caused by fibrocystic changes — formation of fluid-filled sacs (cysts) and scarring in the connective tissue that supports the breast.
If a lump or other breast abnormality is cancer, it may be noninvasive or invasive. Noninvasive cancer is a very early cancer that has not spread beyond the duct. Invasive cancer has spread from the duct into surrounding breast tissue and may have spread to the lymph nodes. Metastatic breast cancer has spread from the breast to other parts of the body.
Normal breast with inset showing cells lining milk ducts and lobules (milk-producing glands), where breast cancer often begins. Figure on right shows lymph nodes and lymphatic vessels that carry lymph, a clear fluid. Cancer cells often enter lymphatic vessels and travel to the underarm (axillary) lymph nodes.
Invasive breast cancers include:
Other, relatively rare types of invasive breast cancer that have a better prognosis — meaning expected outcome — than the invasive cancers listed above are medullary carcinoma (accounting for 5 percent of breast cancers), tubular carcinoma (accounting for 2 percent) and mucinous carcinoma. Paget's disease of the nipple is cancer that spreads from the breast ducts into the skin of the nipple and the areola, the dark area around the nipple. It accounts for 1 percent of breast cancers. Phyllodes tumor is an uncommon breast tumor that forms in the stroma, or connective tissue of the breast.
Tests such as mammography, or X-rays of the breast, allow doctors to see tiny growths which may not ever spread to other tissues. These noninvasive growths, in which cancer cells have not broken through the duct into other parts of the breast, account for 15 percent to 20 percent of the breast "cancers." Other terms that are used for noninvasive breastcancer are carinoma in situ or Stage 0 breast cancer.
Noninvasive breast cancers sometimes change over time into invasive disease. Decisions about how to treat noninvasive breast cancer are based on their potential for change.
Noninvasive breast cancers include:
Reviewed by health care specialists at UCSF Medical Center.
This information is for educational purposes only and is not intended to replace the advice of your doctor or health care provider. We encourage you to discuss with your doctor any questions or concerns you may have.
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