Cyst Symptoms and Causes
Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: William C. Shiel, Jr., MD, FACP, FACR
A cyst is a closed sac- or bladder-like structure that is not a normal part of the tissue where it is found. Cysts are common and can occur anywhere in the body in persons of any age. Cysts usually contain a gaseous, liquid, or semisolid substance. Cysts vary in size; they may be detectable only under a microscope or they can grow so large that they displace normal organs and tissues. The outer wall of a cyst is called the capsule.