Vertebra plana: benign or malignant lesion?

The case of a 9-year-old boy presenting with a vertebra plana at T7 is reported. The initial diagnosis, as suggested by clinical presentation, conventional radiographs and CT scans, was eosinophilic granuloma. Positive radionuclide bone scan led to biopsy of the posterior arch, which suggested giant cell tumour. MRI showed extraspinal tumour involvement. Vertebrectomy revealed osteosarcoma.