• Definition: benign mucin-filled cyst that develops along tendons or joints and has no true epithelial lining
• Epidemiology: most common type of hand mass
• Location: wrist and fingers (most common at the dorsal wrist)
• Pathophysiology: herniation of connective tissue associated with repetitive trauma and mucoid degeneration of periarticular structures → sac that is lined with synovial cells and contains paucicellular connective tissue (typically mucin)
• Clinical features
  • Usually asymptomatic but can occasionally cause joint pain
  • Fluctuant, transilluminant swelling
  • Can lead to nerve compression, which may cause numbness, weakness, or tingling (e.g., Guyon tunnel syndrome)