"Aggressive" osteoblastoma of the maxilla.

A case of osteoblastoma in the maxilla of a 6-year-old boy is reported. The tumor was clinically characterized by locally aggressive behavior but histologically consisted of a relatively well-circumscribed mass of bone-producing epithelioid osteoblasts and occasional multinucleated osteoclasts characteristic of osteoblastoma. Radiographically the tumor appeared to penetrate the cortical plate. Because of the size of the lesion, its histologic features, and the clinical and radiographic impression of its being poorly confined, the diagnosis of "aggressive" osteoblastoma was rendered. The problem of differentiating between benign and aggressive forms of osteoblastoma is discussed.