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:
- also known as eburnated osteoma
- dense bone lacking Haversian system
- also known as osteoma spongiosum
- resembles 'normal' bone, including trabecular bone often with marrow
- 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.
Treatment and prognosis
Osteomas are benign and only require excision if they cause adjacent complications (e.g. mucocoele formation) or mass effect (functional or cosmetic impairment).
- 1. Maroldi R, Nicolai P, Antonelli AR. Imaging in treatment planning for sinonasal diseases. Springer Verlag. (2005) ISBN:3540423834. Read it at Google Books - Find it at Amazon
- 2. Erdogan N, Demir U, Songu M et-al. A prospective study of paranasal sinus osteomas in 1,889 cases: changing patterns of localization. Laryngoscope. 2009;119 (12): 2355-9. Laryngoscope (full text) - doi:10.1002/lary.20646 - Pubmed citation
- 3. Wenig BM. Atlas Of Head And Neck Pathology. Saunders. (2008) ISBN:0721697887. Read it at Google Books - Find it at Amazon
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.
- bone-forming tumours
- cartilage-forming tumours
- chondromyxoid fibroma
- fibrous bone lesions
- bone marrow tumours
- other bone tumours or tumour-like lesions
- aneurysmal bone cyst
- benign fibrous histiocytoma
- giant cell tumour of bone
- Gorham massive osteolysis
- haemophilic pseudotumour
- intradiploic epidermoid cyst
- intraosseous lipoma
- musculoskeletal angiosarcoma
- musculoskeletal haemangiopericytoma
- primary intraosseous haemangioma
- simple bone cyst
- impending fracture risk