A myxoid cyst, also known as a synovial cyst or a mucoid cyst, is not a dangerous condition. In this condition, fluid from degraded connective tissue forms a lump on a finger or toe. This type of cyst may indicate that the patient has osteoarthritis, but this is not always the case. Though a myxoid cyst can be treated relatively easily, it can return.
Most often, a patient will have a myxoid cyst on a finger, but in some cases, a toe is affected. It is almost always present on the last segment of the finger or toe, usually only a centimeter (0.4 inches) or less from the nail on one side. The nail can also develop an indented groove due to the presence of the cyst. In rare cases, this type of cyst can affect the fingertip, and some cysts may also grow under the nail itself.
The cyst is a skin-colored, round lump with a shiny, almost translucent surface, and inside the lump is a collection of thick, sticky fluid. This fluid, tinted a slight yellow or pink, is thought to come from the breakdown products of a joint. Most people only have one myxoid cyst at any one time, and if more than one are present, they are usually on different fingers.
As the cysts are produced by old joint tissue, the most common age for developing the condition is at 60 and over. The cysts are harmless and not infectious. Normally, the lumps do not cause any pain, but they can be damaged through regular activities and become more sensitive.
They can be unsightly, and relatively simple procedures can treat the problem. Squeezing the fluid out of the cyst, lancing it with a sterile needle, or compressing the cyst can all help to flatten the lump. Freezing the cyst off with liquid nitrogen or injecting it with medications such as steroids are other options, and surgical removal is also possible. Despite these treatments, however, myxoid cysts may return. Some cysts also disappear on their own over time.
Antibiotic treatment is only necessary if a cyst becomes red and painful after becoming infected. The presence of a cyst does not necessarily indicate that the patient has osteoarthritis, but it is possible. If osteoarthritis is the cause, then the cyst occurs because the lining of the joint has protruded out from the joint to the surface of the skin.