A cyst is a sac-like pocket of tissue containing fluid or other substances. It can grow almost anywhere in the body under the skin. With many forms of cysts comes many treatment options. Small cysts do not usually need treatment, but can be readily removed by a minor surgical procedure. Cysts can remain untreated for years. Larger cysts are usually removed if they become painful, draining, inflamed, or infected. Cysts are treated by making a small surgical opening into the skin and removing the sac and its contents. This procedure is called an excision. This is done under local anesthetic all within the dermatology clinic and may require stitches, which are removed a few days later. Occasionally cysts recur and need further treatment.