Synonyms

• Ivory exostosis
• peripheral osteoma

Category

Bone

Behaviour

Benign

Gender

Both equally

Tissue of Origin

Bone

Epidemiology

• Common Benign Bone-forming lesion
• Peak incidence in 4th–5th decades
• No significant sex predilection
• Gardner Syndrome: multiple osteomas + colonic polyposis + soft tissue tumours

Clinical Features

• Asymptomatic bony protuberance - most often incidental
• Sinuses: headache, sinusitis, proptosis if orbital
• Gardner Syndrome: multiple osteomas + desmoid tumours + colonic polyps (risk of colorectal carcinoma)
• Jaw osteomas: malocclusion

Location

• Paranasal sinuses (frontal sinus most common)
• Calvarium/skull
• Mandible and maxilla
• Long Bones (rare - periosteal osteoma)

Imaging

• Dense, well-defined, ivory-like bony lesion on X-ray/CT
• No aggressive features, no periosteal reaction
• CT: homogeneous dense Bone, no soft tissue component
• MRI: Low signal on all sequences (cortical Bone)

Pathology

• Compact lamellar Bone with haversian systems (ivory osteoma)
• Or cancellous Bone with fatty marrow spaces (spongy osteoma)
• No cellular atypia
• APC mutation in Gardner Syndrome-associated osteomas

Genetics

• Gardner Syndrome: APC germline mutation (5q21)
• Sporadic osteomas: no specific mutations
• KRAS mutations reported in some paranasal sinus osteomas

Treatment

• Asymptomatic: observation only
• Symptomatic or cosmetically unacceptable: surgical excision - curative
• Gardner Syndrome: colonoscopy surveillance for colonic polyps

Prognosis

• Excellent - no Malignant potential
• Recurrence rare after complete excision
• Gardner Syndrome requires lifelong colonoscopic surveillance

Key Points

• Multiple osteomas should prompt consideration of Gardner Syndrome - refer for APC testing and colonoscopy
• Ivory appearance on CT is diagnostic - no further investigation required for typical asymptomatic lesion
• Frontal sinus is the most common location
• Treatment only required when symptomatic

Workup - Blood Tests

No blood tests required

Workup - Local Imaging

• Plain radiograph
• CT - gold standard; homogeneous dense bone, confirms diagnosis

Workup - Biopsy

Biopsy NOT required - imaging is diagnostic

Workup - Staging

No staging required

Follow-up Summary

• Year 1: Post-operative visit within first 6 weeks; 3–6 monthly clinical examination and plain films of primary site
• Years 2–3: 6-monthly clinical examination and plain films of primary site
• Discharge 3 years after surgery