Localization: Any osseous segment may be affected, but the most common sites are the metadiaphyses of the long bones and the spine.

Clinical: Pain and swelling generally of less than 3 months duration. Frequent reports of a previous trauma in the same skeletal site. Onset or progression of symptoms has been observed in some cases during pregnancy.

Imaging: The characteristic radiographic appearance of ABC is a subperiosteal, poorly defined osteolysis, elevating and inflating the periosteum and progressively eroding the cortex. CT and MRI are often helpful in showing fluid levels within the cyst. Angiograms show intense and persistent accumulation of contrast media. Isotope scan commonly reveals an increased uptake with a cold central area.

Histopathology: Grossly it appears as a blood-filled sponge limited by fibrous septa. The wall of the cystic cavities is not formed by endothelial cells but by mesenchymal tissue rich in fibroblasts, histiocytes, thin capillaries, and scattered multinucleated giant cells. Immature trabeculae of reactive bone may be seen.

Course and Staging: The lesion may progress very rapidly, but in some cases, it may heal spontaneously, after a fracture or a biopsy. Recent cytogenetic data have demonstrated the presence of fusion oncogenes in a subgroup of ABCs. Nevertheless, its origin is controversial; ABC is commonly staged as a benign tumor.

Treatment and Prognosis: After intralesional surgery, local recurrence occurs in 20 % of cases. Radiation therapy (30–40 Gy) has been proven effective in inducing cyst ossification, but it is charged by the risk of sarcoma induction or growth plate damage in children. Selective arterial embolization of the nutrient vessels represents an alternative method in difficult locations (spine or pelvis).