| Noun | 1. | mastectomy - surgical removal of a breast to remove a malignant tumormodified radical mastectomy - removal of a breast and the pectoralis minor and some lymph nodes in the adjacent armpit radical mastectomy - removal of a breast and the underlying muscles (pectoralis major and pectoralis minor) and lymph nodes in the adjacent armpit simple mastectomy - removal of a breast leaving the underlying muscles and the lymph nodes intact |