Breast cancer is the uncontrolled growth of abnormal cells that can develop in one of several areas of the breast, including the
ducts that carry milk to the nipple
small sacs that produce milk (lobules)
Breast cancer is considered invasive when the cancer cells have penetrated the lining of the ducts or lobules. That means the cancer cells can be found in the surrounding tissues, such as fatty and connective tissues or the skin. Noninvasive breast cancer (in situ) occurs when cancer cells fill the ducts but haven't spread into surrounding tissue.
To continue reading this article, you must login
Subscribe to Harvard Health Online for immediate access to health news and information from Harvard Medical School.