Aneurysmal bone cyst: report of a case mimicking orbital tumor.

Aneurysmal bone cysts are rare bone tumors which normally affect the vertebral region or long bones. Involvement of facial bones is uncommon. Although nonneoplastic, these lesions are expansile and may cause local destruction of bone and soft tissues. When making the diagnosis, it is imperative to consider the clinical, radiologic, and histologic features of the entity to avoid confusion with other possibly malignant giant cell tumors. We report an unusual case involving the orbit in a 2 1/2-year-old girl.