Ganglion cysts are noncancerous lumps that most commonly develop along the tendons or joints of your wrists or hands and are typically round or oval and are filled with a jelly-like fluid.
Small ganglion cysts can be pea-sized, while larger ones can be around an inch (2.5 cm) in diameter. Ganglion cysts can be painful if they press on a nearby nerve. Their location can sometimes interfere with joint movement.
Frequently, ganglion cysts will appear on the dorsum of the hand.
It’s not clear what causes a ganglion cyst to develop. It grows out of a joint or the lining of a tendon, looking like a tiny water balloon on a stalk, and seems to occur when the tissue that surrounds a joint or a tendon bulges out of place. Inside the cyst is a thick lubricating fluid similar to that found in joints or around tendons.
Cysts are usually painless. However, if a cyst presses on a nerve — even if the cyst is too small to form a noticeable lump — it can cause pain, tingling, numbness or muscle weakness. The cyst may restrict joint motion or be a source of pain itself if it is getting compressed with motion of the joint.
Ganglion cysts can be aspirated, typically under ultrasound. Sometimes they will be aspirated and then injected with cortisone or possibly a dextrose solution.