Mastectomy is the medical term for the surgical removal of one or both breasts, partially or completely. A mastectomy is usually carried out to treat breast cancer. In some cases, women believed to be at high risk of breast cancer have the operation as a preventive measure. Alternatively, some women can choose to have a wide local excision, also known as a lumpectomy, an operation in which a small volume of breast tissue containing the tumor and a surrounding margin of healthy tissue is removed to conserve the breast. Both mastectomy and lumpectomy are referred to as "local therapies" for breast cancer, targeting the area of the tumor, as opposed to systemic therapies, such as chemotherapy, hormonal therapy, or immunotherapy.