mature osteoma

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

Terminology

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".

Clinical presentation

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:

Pathology

Osteomas are, as the name suggests, osteogenic tumors composed of mature bone. Three histological patterns are recognized :

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

    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.

    Treatment and prognosis

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