Mucous Cysts are a very common cause of finger masses over the small finger joint closest to the tip. Mucous cysts are a type of ganglion cyst that usually arises because of an underlying arthritis of that joint. Initial treatment is by aspirating the cyst. Please don’t try this yourself. The cyst connects to the underlying joint, and if an infection occurs it can spread to the underlying joint, causing a serious problem. Injecting steroids has not been shown to increase the cure rate, and may predispose to an infection.
Following aspiration, approximately half of the mucous cysts return. As mucous cysts are benign they can often be observed without further treatment. However, if the skin over the cyst starts to thin, predisposing to joint infection, the cyst should probably be removed. If the skin thins enough, a local flap (soft tissue rearrangement) may become necessary. In addition, many people don’t like the way the cyst looks and desire to have them excised. In addition, the cysts often cause a nail deformity. Removing the cyst can improve or resolve the nail deformity in 60-100%, depending on how long the deformity has been present.
It is important to understand that in order to permanently remove the cyst, the underlying joint must be addressed. Many dermatologists and non-hand surgeons often just try to just cut out the cyst or freeze it. These inadequate techniques don’t usually work very well and recurrences are common. As for wrist ganglions, the joint capsule around the joint must have a section removed to prevent reformation of the one-way valve that causes these cysts in the first place (see the Ganglion Cysts section for more information). In addition, any bone spurs from the joint’s arthritis should be partially removed to open up the space created around the joint. This prevents re-scarring of the tissues around the joint, which leads to the recreation of a one-way valve and a recurrence of the cyst. This surgery should probably be performed by a fellowship-trained hand surgeon, as injury to the tendons, ligaments, and/or nail bed about the joint, with resultant deformity, may occur when surgery in this area is performed by those less well-versed in the anatomy and techniques of hand surgery.
If the skin over the cyst has become very thinned, a flap may be required to provide adequate soft tissue coverage over the joint. This requires rearranging some of the skin and underlying fat on top of the finger, but does not cause any additional pain or down-time.
Mucous cyst excision is an outpatient procedure that is very successful. There are no formal activity restrictions after surgery, and down-time is minimal. The dressing can be removed after 5 days and showering and most activities resumed. Just blot the wound dry and cover it with a Band-Aid. Don’t submerge the finger under water until the stitches are removed at two weeks. Understand that some of the pain attributed to the cyst may actually be due to the underlying joint arthritis, and that removing the cyst won’t cure that part of the pain.