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HealthInfo West Coast-Te Tai Poutini

What is a ganglion cyst?

Ganglion cystA ganglion is a fluid-filled swelling or cyst that is near a tendon or joint. Ganglion cysts look like a smooth soft lump under the skin. They are formed when some of the jelly-like fluid that is in the joint (called synovial fluid) leaks out. Often we don't know exactly what causes them. Sometimes they also go away by themselves, without any treatment.

Ganglion cysts are most common on the back of the wrist or the top of the foot, but they can happen anywhere. They are not harmful and are not cancer. But if they are large they can sometimes be painful, or can look unattractive.

Usually a doctor can diagnose a ganglion cyst simply by seeing it and you won't need any further tests.

The word "ganglion" can also mean a collection of nerve cells. However this type of ganglion cyst does not refer to that.

On the next page: Living with a ganglion cyst

Written by HealthInfo clinical advisers. Endorsed by clinical directors, Plastic Surgery and Orthopaedics departments, Canterbury DHB. Last reviewed February 2017.

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Review key: HIGGL-13830