Conditions Expert Dr. Otis Brawley Chief Medical Officer,
American Cancer Society

Expert answer

A ganglion cyst, also known as ganglia, is a fluid-filled mass that can occur at any joint, but it most commonly found on the thumb and palm side of the wrist. Other less common sites for ganglion cysts include the base of the fingers, the top of the foot and, even less, the knee, shoulder and spine.

One can usually feel a ganglion cyst. It is usually palpable and painless but can be very painful when the cystic mass places pressure on nearby tendons or nerves. Occasionally, a ganglion cyst can cause a lot of pain, and the mass is not felt. This is called an occult ganglion cyst.

The cyst is filled with a gelatinous clear fluid. The walls of the cyst are tissue of the joint or tissues of a tendon at the joint.

The exact cause of ganglion cysts is not known. Ganglion cysts seem to travel in families, but some seem to be due to degeneration of tissues after repetitive movement. People who have ganglion cysts also tend to be prone to develop more of them.

A ganglion cyst is a common complaint usually handled by a general internist or family practice physician. Only the most complicated cases need to be referred to an orthopedic surgeon or a rheumatologist.

First, the health care provider will do an assessment. A mass or swelling of the wrist can be due to several things. Painful masses are most commonly caused by injury to the ligaments and soft tissues surrounding the joint or the bones that make up the joint.

If the pain and mass follow a traumatic injury, a physical examination and X-rays are needed to distinguish soft tissue injury from damage to cartilage or bone. If the symptoms develop without a history of trauma, X-rays and blood studies may be warranted to rule out rheumatic diseases of the joint.

A health care provider would typically use the following approach to make the diagnosis of a ganglion cyst.

• Transillumination, in which the light of a simple flashlight shines through the cyst. This can be done in-office and will distinguish the ganglion from a solid tumor.

• In patients with wrist pain, no clear transilluminated mass and normal X-ray studies, an MRI can differentiate most ganglia from other types of masses.

• Ultrasound is also used for detecting ganglion cysts in patients with wrist pain of unclear origin.

Untreated ganglia can spontaneously regress and spontaneously recur. Observation is appropriate for a non-painful ganglia that does not interfere with joint movement. When bothersome or symptomatic, treatments include:

• Inserting a needle on a syringe to aspirate or remove the fluid followed by injection of an anti-inflammatory such as a steroid. This works for about 80 percent of patients getting it.

• Injection of a drug, hyaluronidase, into the cyst followed by suction of the fluid out of the cyst. This is effective for 90 percent of patients getting it.

• Surgical removal of the ganglion is far more involved than aspiration, but it is very effective. Less than 5 percent of these patients have a recurrence.