A ganglion cyst is a benign (noncancerous) lump or sac-like swelling that most commonly occurs on the tissues that line the tendons or joints of your wrists or hands. They also may occur in the ankles and feet. They are usually harmless. Ganglion cysts are the most common cyst of the hands and wrists. A ganglion cyst usually appears round or oval in shape and are filled with a jelly-like fluid. Ganglion cysts may be small or large. The larger cysts are usually about an inch in diameter. If a ganglion cyst grows near a nerve and puts pressure on that nerve, they can be painful. Depending on where they are growing, they may disrupt a person’s normal movement, especially within their joints.