A ganglion cyst or mucous cyst is a benign swelling or bump that most commonly occurs on the back-side of the finger towards the last joint of the finger near the fingernail. Although, ganglion cysts can also occur around any part of a finger or thumb when associated with a tendon sheath. A mucous cyst is basically a small sac containing a thick, clear, jelly-like substance that is produced from degenerative arthritis of the last knuckle joint of the finger or thumb called the distal interphalangeal joint (DIP joint) of the finger or interphalangeal joint (IP joint) of the thumb. Sometimes the cysts can be painful, but often these are painless. The cysts are also capable of changing in size, and at times, can simply disappear on their own. However, due to the very thin skin near the fingernail and last knuckle, cysts that tend to enlarge can create problems of skin breakdown or even begin to weep fluid. Additionally, if the cyst migrates towards the fingernail, grooves or deformities to the fingernail can occur from pressure of the cyst against the tissue that is responsible for fingernail growth.
X-rays of the finger are generally done to assess for arthritis of the IP joint which can further confirm the diagnosis of a mucous cyst. If the cyst is small and painless, conservative treatment can be done with observation and patient education. A mucous cyst can disappear spontaneously, but the recurrence rate is typically high. If the mucous cyst is fairly large, becomes painful, or causes skin breakdown, your hand doctor may recommend surgery for excision of the cyst with removal of the arthritic bone spurs. If the skin is of poor quality, a local rearrangement or advancement skin flap of healthy tissue may be necessary to cover the wound. Surgery is generally successful for alleviation of pain and effective in preventing formation of another cyst. Dr. Katz will discuss your problem in detail and help you choose the treatment that is best for you.