Review Question - QID 892

The radiographs and histology are consistent with fibrous dysplasia.

Fibrous dysplasia is a developmental bone abnormality that results from a defect in the gene coding for alpha subunit of Gs, the G protein that stimulates cAMP formation (overproduction of cAMP, causes overexpression of c-fos, which regulates proliferation and differentiation of osteoblasts and osteoclasts). More commonly lesions are found in the medullary cavity.

Leet et al performed a retrospective study on polyostotic fibrous dysplasia and found that the disease had a very a wide clinical spectrum among the patients. The greatest amount of functional limitations were seen in children with a loss of the normal femoral neck-shaft angle and a high disease burden in the lower extremities.

Figures A show san eccentric lesion with a scalloped border and a ground glass appearance consistent with fibrous dysplasia. Figures B and C demonstrate fibrous stroma in a storiform pattern surrounding the immature lamellar bone consistent with fibrous dysplasia.

Incorrect Answers:
1. Adamantinoma: low-grade malignant tumor of unknown etiology that is almost always located in the mid-tibia. Histology shows characteristic fibrous and epithelial tissue in gland like pattern without immature lamellar bone
2. Osteomyelitis: there is no history of trauma or systemic signs of infection. Histology does not show any inflammatory cells.
4. Osteosarcoma: radiographs can usually show blastic and destructive features. Histology will show tumor cells with significant atypia, that produce "lacey" osteoid. Furthermore, stroma cells show malignant characteristics with atypia, high nuclear to cytoplasmic ratio, and abnormal mitotic figures.
5. Stress fracture: lateral xray may show "dreaded black line" and often patient will have vague symptoms that often subside with cessation of activity.