Differential Diagnosis for a Lump on the Dorsal Finger PIP Joint

• Single Most Likely Diagnosis
  • Ganglion cyst: This is the most common cause of a lump on the dorsal finger PIP joint. Ganglion cysts are benign, fluid-filled lumps that often occur on the wrist or fingers and can be associated with joint or tendon irritation.
• Other Likely Diagnoses
  • Rheumatoid nodule: These are firm, painless lumps that can occur on the fingers or wrists in people with rheumatoid arthritis. They are a sign of chronic inflammation.
  • Bouchard's node: This is a bony growth that occurs on the proximal interphalangeal (PIP) joint due to osteoarthritis, leading to a visible lump.
  • Heberden's node: Similar to Bouchard's node but occurs on the distal interphalangeal (DIP) joint, though it can sometimes be confused with a lump on the PIP joint.
• Do Not Miss Diagnoses
  • Malignant tumor (e.g., squamous cell carcinoma, melanoma): Although rare, any new or changing lump should be evaluated for the possibility of cancer, especially if it's growing, bleeding, or changing color.
  • Infection (e.g., abscess, osteomyelitis): An infected lump could be a sign of a serious bacterial infection requiring prompt antibiotic treatment or drainage.
  • Gouty tophus: A deposit of uric acid crystals that can form a lump, often associated with gout. While not usually life-threatening, it indicates a need to manage gout.
• Rare Diagnoses
  • Giant cell tumor of the tendon sheath: A rare, benign tumor that can occur on the fingers, often presenting as a lump.
  • Epidermoid cyst: A benign cyst that can occur anywhere on the skin, including the fingers, though it's less common on the dorsal aspect of the PIP joint.
  • Lipoma: A benign fat tumor that can occur almost anywhere, including the fingers, but is less common in this specific location.