Fibroma

Ossifying fibroma

• Rare
• Of heads of horses and cattle
• Grossly:
  • Sharply demarcated expansive mass
  • Distort normal bone contour
• Histologically:
  • Dense fibrous tissue
  • Bone spikules of woven bone covered by osteoblasts
  • In later stages resembles osteoma
• Malignant transformation has not been reported