Multicentric Osteoid Osteoma Presenting a Diagnostic Dilemma

We present a case of a relatively common benign tumor that was a diagnostic dilemma because of its atypical appearance in multiple imaging modalities. Our patient was a 22-year-old man who presented with complaint of three months of shin pain with running. The radiographically demonstrated sclerotic lesion in his right tibia initially was thought most likely to be a stress fracture, but on further evaluation, it had features that suggested a subacute osteomyelitis or Brodie's abscess with focal sequestra. It was in fact, biopsy proven to be an osteoid osteoma with multiple, closely adjacent nidi. Its elongate, multicentric, "string of beads" arrangement as well as its intramedullary location is uncommon and it was larger than normally expected. Because of the unusual presentation and appearance of this lesion it caused a diagnostic dilemma. This lesion was evaluated with a full spectrum of modalities including radiographs, CT, MRI, Technetium 99m-MDP bone scan and Indium-111 white blood cell scan. After biopsy achieved a definite diagnosis, this tumor was successfully treated with radiofrequency ablation of all nidi in one session.