Aggressive osteoblastoma.

The clinical, radiological and pathological features of two cases of an osteogenic tumour with long survival are described. The tumours have the histological pattern of benign osteoblastoma with other more cellular and aggressive features suggestive of a low grade osteosarcoma. They are locally invasive but the absence of metastases indicates that separation from both entities is justified clinically and pathologically. The term aggressive osteoblastoma is suggested.