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Osteomas are benign bone tumors that most commonly occur in the head. When occurring in the medullary cavity osteomas are called bone islands 5.
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Osteoma is the preferred terminology with ivory exostosis, parosteal osteoma, and maxillary/mandibular torus not recommended per the WHO classification of soft tissue and bone tumors (5th edition) 5.
Osteomas are common with an equal male/female distribution 5.
Diagnostic criteria according to the WHO classification of soft tissue and bone tumors (5th edition) 5:
essential: bone tumor with compatible imaging; tumor arises on the bone source or within the medullary cavity; composed of lamellar/cortical-type bone
These lesions are benign, slow growing, and usually asymptomatic. They may be incidentally identified as a mass in the skull or jaw, or as the underlying cause of sinusitis or paranasal sinus mucocele 5.
Osteomas are benign osteogenic tumors composed of lamellar/cortical-type bone. The etiology is unknown 5.
Osteomas most commonly occur in bones formed in membrane, almost exclusively occurring in the head 5, with the most common locations including:
These are well-cirumscribed tumors broadly attached to the bone surface 5.
Two histological subtypes are recognized: compact and spongious. In cancellous bone, the bone marrow is filled with a well-vascularized and moderately cellular and fibrous stroma with inconspicuous osteoblasts and osteocytes and absent inflammatory infiltrate 5.
when multiple, Gardner syndrome should be considered 5
Plain radiograph / CT
Osteomas appearing ivory-like as round, very radiodense lesions, similar to the normal cortex 5. Mature osteomas may demonstrate central marrow ref.
T1: low signal
T2: low signal 5
Mild uptake may be seen on bone scintigraphy 5.
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). They can slowly grow 5.
History and etymology
Osteomas have been documented as far back as 664-332 BCE in ancient Egypt 5.
Considerations include many cranial and facial bone lesions 6:
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- 6. Tarsitano A, Ricotta F, Spinnato P et al. Craniofacial Osteomas: From Diagnosis to Therapy. J Clin Med. 2021;10(23):5584. doi:10.3390/jcm10235584 - Pubmed