Tuesday 23 November 2004
Some osteomas appear on the outer surface of the calvaria as circumscribed, ivory-like excrescences composed of mature lamellar bone.
Similar surface osteomas on the long or flat bones are very rare and most likely initially diagnosed as surface osteogenic sarcoma.
However, microscopic examination will reveal only mature bone without any associated low-grade fibrous component and usually only non-descript adipose tissue in the marrow spaces.
Osteomas seen on the face are generally associated with the frontal and ethmoid sinuses, and are formed of dense immature woven bone, often with a central area characterized by fibrosis with active osteoblasts and osteoclasts.
The lesion does not recur after surgical excision, and it is not associated with malignant change.
well-circumscribed nodular growth
the lesion is composed of mature lamellar bone
irregular heavily mineralized mass
The lesion has a dense appearance.
The lession is well demarcated from the adjacent cancellous bone.
compact cortical bone
Very rarely, this latter type of osteoma is associated with colonic polyps (Gardner’s syndrome).
Gardner syndrome is an autosomal dominant genetic disorder, and it is of particular importance because of the malignant change that frequently occurs in the adenomatous intestinal polyps.
Gardner syndrome is associated with mutations on the APC gene on chromosome 5.
- lamellar bone-forming tumors
- spongious bone-forming tumors