A mastectomy is surgery to remove a whole breast. It is used to treat breast cancer. A total (or simple) mastectomy removes only the breast. Other types of mastectomy may involve removing the breast plus nearby tissues, such as lymph nodes under the arm. This may be needed if cancer has spread to these areas. In some cases, it may be possible to leave most of the skin that was over the breast (skin-sparing mastectomy) or the skin plus the nipple and areola (nipple-sparing mastectomy).

If a person has a very high risk of getting breast cancer, the breasts may be removed before cancer is diagnosed. This is called a prophylactic mastectomy. It can help prevent breast cancer.