Aneurysmal bone cyst is a benign, but locally invasive (can go into soft tissue), bone lesion with multiple cystic blood-filled cavities. It typically affects pediatric patients (age range 10-20 years). Girls are affected more than boys.

It most often presents in the metaphysis of long bones, the spine, and the pelvic bone but can occur in any bone. When an aneurysmal bone cyst develops in the spine, it is more common in the posterior elements, but it can occur in the vertebral body.

Aneurysmal bone cyst is characterized by pain and inflammation, usually at a single site. Depending on the location and size of the cyst, signs and symptoms may include swelling, limping, pathologic fracture, mild hemorrhaging, and/or neurologic findings. It is usually discovered on x-ray.

It may be associated with other tumors.

Although it is benign and does not metastasize, the cyst can be locally destructive and requires referral to a specialist.