Ganglion Cysts Are Fluctuant
Ganglion cysts are characteristically fluctuant (compressible) rather than fixed, as they are fluid-filled lesions that can be confirmed by transillumination and aspiration. 1
Physical Examination Characteristics
Ganglion cysts present as soft tissue swellings that are:
- Fluctuant and compressible due to their fluid content
- Transilluminable (light passes through the cystic fluid)
- Mobile relative to deeper structures but may have a stalk connecting to the joint
- Smooth and well-circumscribed 2
The fluctuant nature is a key distinguishing feature that helps differentiate ganglion cysts from solid masses during clinical examination. Ultrasound is particularly useful for confirming fluid content in suspected ganglion cysts in the appropriate clinical setting 1, which directly validates their cystic, non-solid character.
Diagnostic Confirmation
When examining a suspected ganglion cyst, look for:
- Transillumination: The cyst should allow light to pass through, confirming fluid content
- Aspiration: Yields thick, gelatinous fluid (mucoid material) 3
- Mobility: The mass should be separate from skin but may have a thin stalk communicating with the joint space 2
Common Pitfall
Do not confuse the presence of a connecting stalk (which may make the cyst feel somewhat tethered to deeper structures) with the cyst itself being "fixed." The cyst contents remain fluctuant even when there is an identifiable connection to the joint 2. The fluctuant quality refers to the compressibility of the fluid-filled mass itself, not its mobility relative to surrounding tissues.
US imaging demonstrates these lesions as homogeneously T2-hyperintense (on MRI) or anechoic (on ultrasound), confirming their fluid-filled nature 1, 2. This fluid content is what makes them fluctuant rather than firm or fixed on palpation.