Adamantinoma of the tibia in a nine-year-old child.

Adamantinoma of the long bones is a rare, low-grade malignancy with a marked predilection for the tibia and is usually seen in patients during the second to fifth decades of life. Adamantinomas have also been reported in children, but the histological pattern in this age group is different from that seen in adults. We report a case of adamantinoma of the tibia in a 9-year-old boy. Histologically, the lesion was osteofibrous dysplasia with an epithelial component, called "differentiated adamantinoma". An osteofibrous dysplasia-like adamantinoma (differentiated adamantinoma) may be the precursor lesion of the classic type of adamantinoma.