Ganglion cysts are very common lumps within the hand and wrist that occur adjacent to joints or tendons. The most common locations are the top of the wrist, the palm side of the wrist, the base of the finger on the palm side, and the top of the end joint of the finger. The ganglion cyst often resembles a water balloon on a stalk, and is filled with clear fluid or gel.
The cause of these cysts is unknown although they may form in the presence of joint or tendon irritation or mechanical changes. They occur in patients of all ages.
These cysts may change in size or even disappear completely, and they may or may not be painful. These cysts are not cancerous and will not spread to other areas.
The diagnosis is usually based on the location of the lump and its appearance. They are usually oval or round and may be soft or very firm. Cysts at the base of the finger on the palm side are typically very firm, pea sized nodules that are tender to applied pressure, such as when gripping. Light will often pass through these lumps, (trans-illumination) and this can assist in the diagnosis. Your physician may request x rays in order to look for evidence of problems in adjacent joints. Cysts at the far joint of the finger frequently have an arthritic bone spur associated with them, the overlaying skin may become thin, and there may be a lengthwise groove in the fingernail just beyond the cyst.
*Source: American Society for Surgery of the Hand - http://www.assh.org