Osteoid osteoma and osteoblastoma: reclassification of 43 cases using Schajowicz's classification.

Forty-three cases of benign osteoblastic tumour of bone from the University of British Columbia bone tumour registry have been reviewed and reclassified according to the classification of Schajowicz and Lemos. Their classification has the advantage that the relationship of the two lesions is recognized and overlap, both radiologically and microscopically, is allowed for. The terminology used in the new classification, however, is cumbersome and confusing and appears to be of no great advantage. We therefore recommend instead the terminology modified from that of Dias and Frost, which incorporates the observations put forth by Schajowicz and Lemos: (a) cortical osteoblastoma, (b) medullary osteoblastoma, (c) periosteal osteoblastoma and (d) multifocal osteoblastoma.