Common Bone Cysts in the Hand
Primary Diagnosis: Ganglion Cysts
Ganglion cysts are by far the most common cystic lesions of the hand, arising from joints, tendon sheaths, and ligaments throughout the hand and wrist. 1, 2 These are not true bone cysts but rather soft tissue lesions that are the predominant "cystic" pathology encountered in hand practice.
Clinical Presentation
- Ganglion cysts present as palpable, often fluctuant masses that may be asymptomatic or cause pain depending on location and size 1, 2
- They can develop at any joint or tendon sheath in the hand, with the dorsal wrist being the most common location 3
- Rapid progression of swelling, warmth, fever, or purulent drainage should raise concern for infection rather than simple ganglion cyst 1
Diagnostic Approach
- Diagnosis relies primarily on history and physical examination, with ultrasound as the first-line imaging modality to confirm the fluid-filled nature 1, 2, 3
- Ultrasound provides 94% sensitivity and 99.7% specificity for superficial soft-tissue masses, reliably differentiating cystic from solid lesions 1
- High-frequency transducers (≥10 MHz) are essential for optimal resolution 1
- MRI is reserved for suspected occult ganglion cysts (non-palpable but symptomatic), atypical ultrasound findings suggesting solid components, or deep-seated lesions in anatomically complex areas 1, 2, 3
- CT is not indicated for characterizing cystic structures already identified on ultrasound and provides unjustified radiation exposure 1
Management
- Surgical excision is the most effective treatment for preventing recurrence, with recurrence rates of 7-39% 3
- For conservative management, follow-up with physical examination with or without ultrasound every 6-12 months for 1-2 years ensures stability 1
- MRI should be repeated at least every 6 months until resolution for patients with persistent symptoms 1, 3
True Bone Cysts: Rare in the Hand
Unicameral (Simple) Bone Cysts
- Unicameral bone cysts are fluid-filled lesions that typically involve long bone metaphysis, primarily the proximal humerus and proximal femur—not the hand 4, 5
- These are seen in children and adolescents, often presenting with pathological fracture 4, 6
- They resolve spontaneously between adolescence and adulthood 4
- In the phalanges of the hands and feet, malignancy is extremely rare, but central cartilaginous lesions should be considered atypical cartilaginous tumors unless proven otherwise 7
Aneurysmal Bone Cysts
- Aneurysmal bone cysts are expansive, hemorrhagic, blood-filled multicameral lesions that are metaphyseal and eccentric, but rarely occur in the hand 4, 8
- They predominantly affect children and young adults, with 70% being true neoplasms and 30% secondary to other bone lesions 8
- MRI shows characteristic fluid-fluid levels 4, 8
- Recurrence is more common in patients under 5 years (34.38% vs. 19.03%) and those with pathological fractures (40% vs. 18.42%) 9
- Treatment options include curettage with adjuncts, image-guided sclerotherapy, or Denosumab 8
Differential Diagnosis Considerations
Subchondral Cysts in Hand Osteoarthritis
- Plain radiographs show subchondral cysts as a classical feature of hand osteoarthritis, along with joint space narrowing, osteophytes, and subchondral sclerosis 7
- These target the DIP joints, PIP joints, thumb base, and index/middle MCP joints 7
- Subchondral erosion occurs specifically in erosive hand osteoarthritis 7
Critical Pitfall
Do not confuse ganglion cysts (soft tissue, periarticular) with true intraosseous bone cysts (unicameral or aneurysmal), which are exceedingly rare in hand bones. The term "bone cyst" in hand pathology almost always refers to subchondral cysts seen in osteoarthritis on radiographs, while palpable "cysts" are ganglion cysts. 7, 1, 4