An aneurysmal bone cyst is named for its aneurysm-like expansion, resulting from localized destructive lesions accompanied by periosteal reactive bone deposition. It represents a blood-filled osteolytic cystic lesion that expands outward from the bone. Its interior is filled with blood and separated by fibrous tissue containing fibroblasts, osteoclast-like giant cells, and reactive woven bone. It is most commonly seen in adolescents and typically occurs in the metaphyseal regions of long bones, such as the proximal humerus, and in the spine.
Clinical Features
Pain and swelling are the primary symptoms, with most patients seeking treatment due to pathological fractures. Radiographically, it appears as an eccentric, balloon-like, radiolucent, expansile, cystic lesion with lytic changes in the diaphysis or metaphysis of long bones. Its margins are well-defined and may include bone septa, giving the cavity a honeycomb or soap-bubble appearance. In some cases, the lesion can also be centrally located.
Treatment
Curettage followed by bone grafting is the primary treatment approach. Preoperative assessment needs to account for the potential risk of significant bleeding. For lesions in locations such as the spine, where surgical excision is challenging, radiotherapy may be utilized and has shown favorable outcomes. However, in children, radiotherapy carries the risk of damaging the growth plate and potential malignant transformation.