Lumpectomy (also called breast-conserving surgery) is surgery to remove a breast cancer tumor (the lump) and the rim of healthy tissue surrounding it (called the margin).  Unlike mastectomy, which removes the entire breast, lumpectomy removes only the cancer to preserve as much of your breast as possible. Lumpectomy can cause cosmetic changes to the breast, such as visible indentation, a tight scar, or distortions in the nipple’s appearance.