Nonossifying Fibroma
AKA: Nonosteogenic fibroma, fibroxanthoma, xanthogranuloma of bone

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• 30 to 40% children over two years have one or more lesions
• Most common between 8-20 years of age
• Usually occur in metaphysis of one (75%) or more (25%) of the tubular bones

• Most often occur in lower extremities around knee
  • Fewer than 10% occur in upper extremities
• Characteristics
  • Geographic
  • Lytic
  • Multilobulated
  • Metaphyseal
  • Usually intramedullary
  • Eccentric
  • Well-marginated
  • Sclerotic rim
  • Endosteal scalloping
• Most lesions heal spontaneously by being replaced with normal bone
  • Migrate away from epiphysis
• May undergo pathologic fracture or rarely cause rickets
  • Do not undergo malignant transformation