| Etiology | Unknown |
| Clinics | It is characterized by a broad clinical spectrum, varying from the more frequent solitary (monostatic) asymptomatic lesion to extensive and severe multifocal (polyostatic) lesions. The monostotic variant most commonly affects the ribs, femur and tibia of older children and young adults. The less frequent polyostotic type may be associated with endocrine abnormalities, skin hyperpigmentation and soft tissue myxoma (so-called Albright syndrome). On radiographs, fibrous dysplasia presents as a well defined osteolytic lesion with benign features, centered within the medulla, and frequently bordered by a shell of reactive sclerosis. Depending on the relative proportion of osseous to fibrous tissue, the lesion can be completely lytic or, most typically, show a relatively high density, the so-called Œground-glass' appearance in a least part of it. Especially in bones with small diameter and flat bones, fibrous dysplasia frequently expands the bone. |
| Pathology | Microscopically, irregular trabeculae of woven bone are embedded in a moderately cellular fibrous matrix. The bony trabeculae have variable and irregular shapes. Osteoblastic rimming of the trabeculae is characteristically inconspicuous and some of the trabeculae seem to emerge from the surrounding fibrous background, suggesting a 'metaplastic' process. Benign lesions that histologically can be confused with FD are osteofibrous dysplasia of long bones and desmoplastic fibroma. Cases of FD with extensive cartilaginous differentiation may be mistaken histologically or radiologically for a benign chondroblastic tumor, although the adjacent fibro-osseous component allows this distinction. The most important differential diagnosis of FD is with low grade (well-differentiated) central osteosarcoma. Rarely sarcomas can arise in FD and some of them occur in patients that had received radiation therapy (post-radiation sarcomas) . |
| Treatment | It should be conservative |
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