radical mastectomy (RA-dih-kul ma-STEK-toh-mee)
Surgery for breast cancer in which the breast, chest muscles, and all of the lymph nodes under the arm are removed. For many years, this was the breast cancer operation used most often, but it is used rarely now. Doctors consider radical mastectomy only when the tumor has spread to the chest muscles. Also called Halsted radical mastectomy.