In light of these developments, dysplastic lesions are thought to consist of an excess of pre-osteogenic cells producing a disorganized collagenous matrix. The few mature osteoblasts present create abnormal bone matrix. The radiographic findings of fibrous dysplasia can be distinctive. Individual lesions can appear as a lucent area with a sclerotic rim. The affected bone can be locally expanded.
Calavarial lesions are usually lytic and multilocular with sclerotic margins.
In the skull base and facial bones, fibrous dysplasia manifests as marked sclerosis and bony thickening. The sinuses may be obliterated. Long standing disease can result in bowed and deformed bones. Pathologic fractures are seen. The majority of lesions in fibrous dysplasia are tracer avid on Tc-99m MDP bone scans.