Ganglion cysts are a non-cancerous mass or lump the usually occur in the back or front of the wrist or in the fingers. They are fluid-filled capsules that arise from joint linings or tendon sheaths. They may arise from underlying joint injury or arthritis. They are benign, often painless and many do not require treatment. However, if the cyst is painful or interferes with normal function, it may be made smaller by removing the fluid with a needle (aspiration), or removed surgically.