Diagnosis: Fibrous Dysplasia
• Fibrous dysplasia is a dysplastic condition of the bone-forming mesenchyme. It is characterized by the inability to produce mature bone, either at a single skeletal site (monostotic form) or at multiple locations (polyostotic form).
• The ribs, facial bones, and long bones are most commonly involved.
• Radiologically, fibrous dysplasia manifests as an intramedullary lesion, showing various degrees of opacity depending on the amount of bone formed and having a typical ground-glass appearance.
• Fibrous dysplasia causes bone expansion, often thinning one cortex, without associated soft tissue mass or periosteal reaction.
• Histologically, the stroma is fibrocellular with bland oval spindle cells and contains maloriented, curvilinear trabeculae typically composed of woven bone, without a recognizable border of osteoblasts. Round, calcified, cementumlike spherules are commonly seen, especially in facial bone lesions.
