Benign (not cancerous) fluid-filled lumps that occur in the breast may be cysts. Breast cysts often change with your menstrual cycle and hormones. Cysts can be painful and present as a lump in your breast. Cyst aspiration often relieves the pressure that may be felt when cysts become large and uncomfortable. Ultrasound guidance is used to locate the cyst in the breast. Local anesthesia is injected. A small needle is then inserted into the breast cyst, and the fluid is aspirated (drawn back) to relieve the pressure. This is a simple outpatient procedure. A cyst aspiration takes about 1 to 1½ hours.