Ganglion cysts are commonly encountered in the general population. They are fluid-filled cavities that occur most commonly on the dorsal aspect of the hands. They are believed to be derived from the synovial lining of various tendons. They typically manifest as asymptomatic, soft, rubbery nodules below the skin.
Clinical Findings: Ganglion cysts are common benign growths that occur on the distal upper extremity in most cases; they are almost always located on the dorsal aspect of the hand or wrist. Ganglion cysts are almost always solitary, but some patients present with more than one, and occasionally the individual ganglion cysts coalesce into one large area. Most are relatively small, 1 cm in diameter, but some can get very large (2-3 cm). The overlying epidermis is normal, and the cyst is located in the subcutaneous space below the adipose tissue. They are smooth, dome-shaped, fluid-filled cysts that are slightly compressible. The cyst is a direct extension of the synovial lining of the tendon. The cysts form by various mechanisms and fill with synovial fluid. This fluid is critical in the normal lubrication of the tendon space to decrease friction and allow the tendon to easily slide back and forth within its synovial covering. These cysts can occur at any age, but they are much more common in the younger population and often manifest in the third or fourth decade of life. Women are much more likely than men to develop these cysts.
Most cysts are asymptomatic, but they can cause discomfort and pain if they become large enough to press on underlying structures. Rarely, the cyst compresses an underlying nerve, resulting in symptoms of numbness or muscle weakness. The differential diagnosis is limited, and most often the diagnosis is made clinically. Occasionally, a biopsy is required to differentiate ganglion cysts from giant cell tumors of the tendon sheath. Giant cell tumors of the tendon sheath are much more likely to be firm in nature. Ganglion cysts have no malignant degeneration potential. In difficult cases, an ultrasound examination can be performed; it is highly sensitive in detecting these fluid-filled cysts.
Pathogenesis: Ganglion cysts are believed to be caused by an outgrowth of the underlying synovial lining of the tendon sheath. Trauma is likely the leading culprit in initiating the formation of these cysts. Patients with osteoarthritis are also at increased risk for development of ganglion cysts, most likely because of the mechanical trauma that the synovial lining repetitively undergoes when it rubs against osteoarthritic bone.
Histology: Ganglion cysts are not true cysts in that they do not have a well-formed epithelial lining that surrounds the entire cystic cavity. The lining is a loose collection of fibrous connective tissue composed mostly of collagen. The cyst lining is multilobulated in most cases and typically has no connection to the underlying joint capsule or tendon sheath. The contents of the cyst are made of mucopolysaccharides.
Treatment: No therapy is required for small, asymptomatic ganglion cysts. If a patient desires removal or if the cyst is causing symptoms, especially weakness and numbness, therapy is needed. Needle aspiration is often used as a first-line treatment option; a pressure bandage is applied to try to keep the cyst from reexpanding. After the aspiration, intralesional injection of triamcinolone is used to try to scar the lining of the cyst. This has shown excellent results. If aspiration and injection are not successful, surgical excision is necessary. It is important to have a hand surgeon evaluate and treat these cysts because of their proximity to multiple vital nerve and tendon structures.