Aggressive osteoblastoma of the maxilla: a case report and review of the literature.

Aggressive osteoblastoma is a rare primary bone neoplasm with the potential for local invasion and recurrence. While the vertebrae or long bones are most commonly affected, few well-documented cases have been reported in the jaws. A 25-year-old man presented with a palatal mass of several months' duration. He reported the lesion had undergone gradual enlargement and, while generally asymptomatic, had recently become increasingly painful. An incisional biopsy was interpreted as "osteoblastic neoplasm" most suggestive of osteoblastoma. However, final diagnosis was deferred until the resection specimen could be evaluated. Following partial maxillectomy, histopathologic examination revealed a proliferation of large epithelioid cells with eccentric nuclei and prominent nucleoli associated with broad, irregular deposits of osteoid and trabeculae of bone. The lesional cells exhibited minimal pleomorphism with infrequent, normal-appearing mitotic figures and numerous osteoclast-like giant cells were observed within an associated loose fibrovascular stroma. Transformation of "blue bone" to more organized eosinophilic trabeculae of woven bone was noted at the periphery of the lesion and there was no evidence of invasion. A diagnosis of aggressive osteoblastoma was made. Previous reports of gnathic aggressive osteoblastoma are reviewed and the features that distinguish this process from conventional osteoblastoma or osteoblastoma-like osteosarcoma are presented.