Ganglion Cyst

Basics

Ganglion cysts are common benign tumors that are not related to nerve tissue (as implied incorrectly by the name).
Can be located anywhere throughout the body but usually adjacent to or within joints and tendons, with the most common locations being the wrist, foot, and ankle
Not a true cyst because microscopic examination does not show an epithelial lining
Most are asymptomatic except for mass effect. Local nerve compression can result in pain, neuropathy, or activity limitation.
Synonyms: synovial cyst; myxoid cyst; Gideon disease; Bible bump

Epidemiology

Can affect all age groups; unusual in children
Most common in ages 20 to 40 years and 3 times as common in women
Common in dorsal wrist, radial wrist, and dorsum of the distal interphalangeal (DIP) joint (referred to as a mucous cyst)
Mucous cysts are usually seen in older patients.
60–70% of hand and wrist ganglion cysts are on the dorsal wrist; 15–20% are on the volar wrist.

Prevalence

Prevalence of wrist ganglia in patients presenting with wrist pain is as high as 19%.
Prevalence of ganglia in patients with a palpable mass in the wrist is as high as 27%.
Reported prevalence in ankles is 5.6%.

Etiology and Pathophysiology

Pathogenesis is unclear. Cysts are filled with mucin and communicate with the adjacent joint space, tendon, and/or tendon sheath via a stalk. Several theories about their origin include:

Herniation of synovial lining creates a one-way valve. Although this is supported by dye studies, the lack of a synovial (epithelial) lining in the cyst wall makes this less likely.
Mucoid degeneration of connective tissue results in formation of hyaluronic acid, leading to cystic space formation. Studies haven’t confirmed this hypothesis.
Joint stress leads to a tear in the joint capsule or tendon sheath allowing synovial fluid to leak into surrounding tissues. Local irritation leads to production of fluid and a pseudocapsule forms (explaining the lack of an epithelial lining).
Recurrent stress may stimulate mucin production by nearby mesenchymal cells (seen on electron microscopy) resulting in cyst formation (1).

Genetics
No specific genetic links have been found.

Risk Factors

Female > male
Osteoarthritis for mucoid cysts
Joint trauma (possible but not proven)

Commonly Associated Conditions

Mucous cysts are usually associated with osteoarthritis at the DIP joint.

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