Osteoblastoma is a benign neoplasm representing approximately 1% of all primary bone tumors. The clinical aspects of the lesion are slow growth swelling, pain, bone expansion and eventual dental displacement. Radiographically, this lesion presents as a mixed radiolucent and radiopaque pattern with definite limits or not. Histologically, it is characterized by the proliferation of osteoblasts, with bone trabeculae set in a vascularized fibrous connective tissue stroma. However, a small group of osteoblastomas presents an aggressive behavior with atypical histological aspects as the presence of greater osteoblasts with increased mitotic activity. The aim of this paper is to report a case of aggressive osteoblastoma and discuss the characteristics of this lesion and its differential diagnosis when compared with other bone lesions. Therefore, a case of a nine years-old girl with a left maxillary swelling for the previous nine months is reported. After clinical and radiographic evaluation, osteoblastoma and osteosarcoma were considered in the differential diagnosis. An incisional biopsy was performed resulting in the diagnosis of osteoblastoma with aggressive behavior. The surgical treatment consisted in the total excision of the lesion with a peripheral osteotomy. After 3 years of treatment no evidence of recurrence was observed.

Conflict of interest: None declared.