A ganglion cyst is a fluid-filled balloon-like mass that develops near joints and tendons. While the exact cause is unknown, it is generally thought that a defect forms in the tissue surrounding a tendon or a joint that allows fluid from one of these areas to penetrate through into the surrounding tissue. This fluid becomes walled off by fibrous tissue that surrounds it, and the cyst forms. It is essentially a balloon of a clear or yellow coloured, thick, jelly-like fluid. It is not uncommon for cysts to grow and retract in size. These cysts are generally benign, and cause few issues on their own, unless the cyst is pushing into sensitive nerve tissue, restricting tendon function, or less commonly constricting a blood vessel.
The initial treatment of ganglion cysts often involves an attempt at drainage. Cysts usually can be drained by introducing a needle into the cyst through the skin and drawing the fluid out, although smaller ones are sometimes difficult to accurately find through the skin. The drainage is often followed by a steroid injection that reduces the inflammation around the cyst and may scar the cyst tissue to prevent regrowth. Unfortunately, this technique does not have a sure chance of keeping the cyst from returning, as the cyst wall and the cyst origin remain in the body. The cyst can refill shortly after it is drained. In these cases, surgical removal is necessary to get rid of the cyst permanently. Through surgery, the entire cyst and its lining is removed, and this significantly lessens the chance of regrowth. There is a chance the cyst can redevelop following surgery, but this is far less than without surgery and drainage alone.