Aneurysmal bone cyst

Aneurysmal Bone Cyst

An aneurysmal bone cyst (ABC) is a benign, but potentially aggressive, bone lesion that typically affects children and young adults. Characterized by its blood-filled, sponge-like spaces, it can cause significant bone expansion and deformity. Despite its name, an aneurysmal bone cyst is not a true cyst, as it does not have an epithelial lining. The etiology of ABCs remains partially understood, with both reactive and neoplastic theories proposed. They are most commonly found in the long bones, vertebrae, and pelvis.

Etiology and Pathogenesis

The exact cause of aneurysmal bone cysts is unknown, but they are believed to result from a combination of genetic, traumatic, and vascular factors. Recent studies have identified USP6 gene mutations in a significant number of ABC cases, suggesting a neoplastic basis. Trauma may also play a role in the development of ABCs by creating a pathway for arterial blood to enter the bone, leading to cyst formation.

Clinical Presentation

Patients with aneurysmal bone cysts often present with pain, swelling, and limited range of motion in the affected area. The symptoms can vary depending on the cyst's size, location, and the presence of pathological fractures. In cases where the spine is involved, neurological symptoms such as numbness or weakness may occur if the cyst compresses nerve structures.

Diagnosis

The diagnosis of an aneurysmal bone cyst is primarily based on imaging studies and histological examination. Radiographs typically show an expansile, osteolytic lesion with well-defined borders and internal septations. Magnetic resonance imaging (MRI) and computed tomography (CT) scans provide further details on the lesion's extent and its relationship with surrounding structures. A definitive diagnosis is made through biopsy, which reveals blood-filled cavities separated by fibrous septa and osteoclast-type giant cells.

Treatment

The treatment of aneurysmal bone cysts varies depending on the lesion's size, location, and the patient's symptoms. Options include curettage and bone grafting, sclerotherapy, and in some cases, surgical resection. Curettage and bone grafting are the most common treatments, offering good outcomes in many cases. Sclerotherapy, which involves the injection of sclerosing agents into the cyst, has emerged as a less invasive alternative with promising results. In extensive or recurrent cases, surgical resection may be necessary.

Prognosis

The prognosis for patients with aneurysmal bone cysts is generally favorable, especially when diagnosed and treated early. However, the lesion has a recurrence rate of approximately 20-30% after curettage and bone grafting. Regular follow-up is essential to monitor for recurrence, particularly in the first few years after treatment.

See Also

• Bone tumor
• Giant cell tumor of bone
• Osteoblastoma
• Osteoclastoma