Fibrous Dysplasia

• In young horse, dogs and cats
• Rare
• Developmental?
• Grossly:
  • Expansive fibro-osseous lesions
  • In metaphyses
  • Firm fibrous masses
  • Gritty when cut
• Histologically:
  • Fibrous stroma with trabeculae of woven bone
  • No recognisable osteoblasts - differentiates from ossifying fibroma
• Radiographically:
  • Smooth edged areas of radiolucency
• Usually resolves
• Lesions in head may cause problems eating or cause pressure on the brain