Adamantinoma of tibia with predominant features of fibrous dysplasia--a case report.

We report a case of adamantinoma of the tibia resembling fibrous dysplasia. The patient was a 55-year-old male, and complained of pain in the right lower leg. Roentgenographs showed a well demarcated osteolytic lesion with small foci of calcification and septation within the diaphysis of the distal tibia. The cortex was partially disrupted. Histologically, initial biopsy specimen showed fibrous connective tissue and trabeculae of immature woven bone, strongly suggestive of fibrous dysplasia. The lesion recurred and the second biopsy revealed nests of spindle cells and tubular epithelial structures embedded in granulation type-fibrous tissue. Immunohistochemically, both the nests of spindle cells and the tubular structures gave a positive reaction for cytokeratin. The present case emphasizes once again that histological diagnosis of fibrous dysplasia of the tibia should be made carefully with exclusion of the possibility of adamantinoma.