​Ganglion cysts are common lumps that are usually found in the hand and wrist. They may occur at the back or the front of the wrist, at the end or base of a finger. They are filled with gelatinous fluid from nearby joints or tendon sheaths. There is no specific cause. Ganglion cysts may be painful when they first appear or when they are at a pressure point. They often change in size and may disappear completely. Ganglion cysts are NOT malignant (cancerous).