Benign osteoblastoma.

Benign osteoblastoma is a benign bone-forming lesion, seen most commonly in the first three decades of life and having a predilection for the vertebral column and the short limb bones. It is distinguishable from osteoid osteoma on the bases of size (being more than one centimetre in diameter) and the absence of surrounding sclerosis. The two lesions, however, are probably of the same origin and behave differently because of their different situations. Treatment is by operation, either excision in whole if practicable, or thorough piecemeal excision and curettage, with bone grafting of the defect if indicated.