Osteoma

Osteomas are benign mature bony growths, seen almost exclusively in bones formed in membrane (e.g. the skull). 

When they arise from bone they may be referred to as a "homoplastic osteoma", and when they arise in soft tissue they may be referred to as a "heteroplastic osteoma".

These lesions are benign, slow growing, and usually asymptomatic. They may be incidentally identified as a mass in the skull or mandible, or as the underlying cause of sinusitis or mucocele formation within the paranasal sinuses. When they are multiple, Gardner syndrome should be considered.

They commonly occur in the head and neck, with the most common locations including:

Osteomas are, as the name suggests, osteogenic tumours composed of mature bone. Three histological patterns are recognised 1:

  1. ivory osteoma
    • also known as eburnated osteoma
    • dense bone lacking Haversian system
  2. mature osteoma
    • also known as osteoma spongiosum
    • resembles 'normal' bone, including trabecular bone often with marrow
  3. mixed osteoma
    • a mixture of ivory and mature histology

The imaging appearance reflects the underlying pathology, with ivory osteomas appearing as very radiodense lesions, similar to the normal cortex, whereas mature osteomas may demonstrate central marrow.

Osteomas are benign and only require excision if they cause adjacent complications (e.g. mucocoele formation) or mass effect (functional or cosmetic impairment).

Bone tumours

The differential diagnosis for bone tumours is dependent on the age of the patient, with a very different set of differentials for the paediatric patient.

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Article information

rID: 4093
Section: Pathology
Synonyms or Alternate Spellings:
  • Ivory osteoma
  • Mature osteoma
  • Mixed osteoma
  • Homoplastic osteoma
  • Heteroplastic osteoma
  • Osteomas

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Cases and figures

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    Case 1: ivory osteoma
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    Axial
    Case 2: ivory osteoma
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    Case 3: ivory osteoma
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    Case 4: mature osteoma
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    Case 5: mastoid osteoma
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    Case 6
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    Case 7: left temporal region
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    Case 8: external auditory canal osteoma
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    Case 9: frontal osteoma
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    Case 10: occipital skull osteoma
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    Case 11: osteoma temporal bone
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    Case 12: parietal skull osteoma
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    Case 13: mandibular osteoma
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    Case 14
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    Case 15: multiple osteomas in Gardner syndrome
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