A mastectomy is the surgical removal of one or both breasts, partially or completely. A simple or total mastectomy is the removal of the entire breast but not axillary lymph nodes (nodes in the underarm area) or muscle beneath the breast. A modified radical mastectomy is the removal of the entire breast and two (of three) levels of axillary lymph nodes in the underarm area. A radical mastectomy is the removal of the entire breast, all lymph nodes in the underarm area and chest wall muscles under the breast.