Cystic Soft Tissue Mass
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
Helpful Clues for Common Diagnoses
Most common cystic-type mass
Filled with gelatinous material of variable viscosity
Occurs alongside joints
Synovial fluid squeezed out from joint through capsular defect
Usually can see cyst point toward nearby joint
Increase in extent through process of cyst enlargement → rupture → consolidation
Fluid-filled mass with stalk extending toward joint
Ovoid or irregular configuration with stalk connecting to joint of origin
No hyperemia except with recent leakage when surrounding tissues may be mildly hyperemic and edematous due to pericystic inflammation
Communication with joint is not always apparent
Locate tell-tale stalk of cyst and trace it toward joint of origin
Inflammation of lining of bursae
Synovial bursae: Constant synovial-lined bursae, which occur in defined anatomical locations
Adventitial bursae: Nonsynovial-lined bursae that are acquired due to friction between opposing parts
Synovial-lined space is not visualized on US unless distended with fluid
Most bursae are accessible to US
US facilitates image-guided aspiration or injection
Bursitis is common, but infective bursitis is uncommon
Chronic bursitis is often associated with wall-thickening and internal debris
Baker cyst = distended semimembranous, gastrocnemius bursa
Helpful Clues for Less Common Diagnoses
