Osteoma

Definition

Asymptomatic, benign, slow growing tumour-like masses, whose histology depends on the site, and that originate from membranous bones.

Aetiology

Osteomas of the facial bones are associated with Gardner’s syndrome

Gardner’s syndrome is autosomal dominant and associated with:

• Intestinal polyposis with frequent malignant change
• Odontomas
• Supernumerary and unerupted teeth
• Soft tissue tumours including fibromas and epidermal inclusion cysts

Incidence

F>M 3:1

Pathology

1. Facial bone osteoma
   * Dense immature bone
   * Often central area with fibrosis with active osteoblasts and osteoclasts
   * Close kinship microscopically with osteoblastoma
2. Calvarium osteomas
   * Circumscribed ivory like tumor composed of mature lamellar bone
   * Can also be seen on long bones and flat bones where radiologically they look like parosteal osteosarcomas.  Parosteal osteomas will not have spindle cells

Clinical

Asymptomatic

May be disfiguring e.g. Jean Claude van Damme

Can block off sinuses and cause chronic sinusitis

Radiology

Well circumscribed, dense lesions, round or oval

Don’t usually grow beyond 2cm in diameter

Can become enormous nearly filling the entire sinus cavity (giant osteoma)

Can be confused with parosteal osteosarcoma

Treatment

If symptomatic, surgical excision.  Recurrence is rare

Most are asymptomatic and don’t require excision

FLAG:  Patients with Gardner’s syndrome may require a prophylactic colectomy