To treat mammary gland hyperplasia in cats, the first step is to perform an ovariohysterectomy. The surgery is usually a lateral cut rather than a midline incision because the mammary glands are too large. Breast hyperplasia will resolve within a few weeks of oophorectomy; mastectomy should be performed if abnormal breast tissue overgrowth causes insufficient blood supply and necrosis, or if breast hyperplasia does not decrease when the source of progesterone is removed.