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Tumor biology and incidence

  • Benign, hamartomatous process
  • Slow-growing lesions of compact bone almost exclusively found in the craniofacial bones, projecting into the oral cavity and sinuses
  • Observed in 3% of patients requiring sinus radographs
  • Primary extracranial osteomas extremely rare; referred to as "parosteal osteomas"
  • Osteoma with cutaneous cysts, fibromatoses, and colonic polyps known as Gardner's Syndrome


Most commonly diagnosed in the fifth decade; age range 16-74 years


M:F = 1:3


Slowly enlarging, hard mass

Associated syndrome

Gardner's Syndrome

Physical findings

  • Palpable mass
  • Lesions in the head may cause:
    • Facial asymmetry
    • Difficulty breathing
    • Eye problems
    • Headache

Plain films

  • Usually grows on the bone surface, but intramedullary cases have been described
  • Outer table of calvarium
  • Frontal and ethmoid sinuses
  • Occasionally long and short tubular bones
  • Variable
  • Extracranial lesions are typically larger than cranial lesions; usually 1-4 cm

AP (left) and lateral tibia. Smoothly contoured, radiodense lesions attached to the cortical surface. Density is uniform and similar to that of cortical bone.

Tumor effect on bone
  • Focal, dense, homogenous bone
  • Well circumscribed geographic borders
Bone response to tumor



Sclerotic matrix

  • Smooth or lobulated surfaces
  • Surfaces merge with underlying cortical bone
Soft tissue mass


CT scan

Axial CT of the tibia

Coronal CT of the tibia


Axial T1 MRI of the tibia

Coronal T1 and T2 MRI of the tibia


Differential diagnosis


  • Gross: Heavily ossified tissue
  • Microscopic: Thickened sclerotic lamellar bone with minimal fibroblastic stroma
  • Etiology unknown
  • Theories:
    • Non-aggressive osteoblastoma
    • Hamartoma of periosteum
    • Terminal ossified phase of fibrous dysplasia

Diagnosis and treatment

  • Excise if symptomatic, or for diagnosis if the lesion is large
  • Complete removal confers a cure


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