Widespread inflammatory response to osteoblastoma: the flare phenomenon. A case of vertebral osteoblastoma caused a diffuse, reactive inflammatory infiltrate in two vertebrae, adjacent ribs, and the paraspinous soft tissues. The authors call this the flare phenomenon. On magnetic resonance images the diffuse inflammatory response caused a misleading appearance that simulated a malignant process (lymphoma or Ewing sarcoma). A computed tomographic myelogram was diagnostic. 