Aneurysmal bone cyst: An unusual presentation of back pain.

Aneurysmal bone cyst (ABC) is a rare benign tumor comprising 1.4% of all primary bone tumors. It commonly involves humerus, femur, tibia, and pelvic bones. Spinal involvement is rare. The pathological appearance of the lesion is one of the blown out distension with fluid filled cavities from which it gains the name aneurysmal bone cyst. The World Health Organization has defined it as an expanding lesion with blood filled cavities separated by septa of trabecular bone or fibrous tissue containing osteoclast giant cells. We describe the case of a 20-year-old Asian male who presented with backache and pain in right leg. Radiology was suggestive of an ABC involving the posterior elements of the lumbar vertebra. Excision was performed. We discuss this unusual case, reviewing the current literature on biological behavior and management of aneurysmal bone cyst.