Ans. is 'c' i.e., Treated by simple curettage Aneurysmal bone cyst Aneurysmal bone cyst occur in children and young adults (5-20 years). The term aneurysmal is used because it causes expansion of overlying coex like vascular expansion of an aneurysm. The metaphysis of long bones is involved most commonly. Most common in femur and tibia; however any long bone can be involved. Other common sites are posterior elements of veebrae and pelvis. athology Cystic spaces of variable sizes & number which are filled with blood but not lined with vascular endothelium. The wall of vascular space is lined with fibroblast cells with collagen, giant cells, hemosiderin & osteoid (secondary to microfractures). Clinical features With expanding lesions, pain may be a presenting feature. Large cyst can also cause swelling Pathological fracture may occur (but less frequent than simple bone cyst). Radiological features of aneurysmal bone cyst Eccentric, expansile osteolytic lesion The characteristic feature is 'blown-out' distension of one surface of the bone. Overlying coex may be intact or disrupted. Extensive sclerosis at the interface between normal and expanded coex (buttersing) may be present. Delicate thin trabeculae is characteristic and an expansile ballooning lesion may produce a 'soap-bubble appearance'. Lesion occurs at metaphysis of long bones. Other common locations include the posterior elements of the spine(pedicle, lamina, transverse process, spinous process) and pelvis. Treatment Surgery is the treatment of choice. Curettage and bone grafting is the procedure commonly followed.