ANEURYSMAL BONE-CYST - A CLINICOPATHOLOGI CAL AND IMMUNOHISTOCHEMICALSTUDY 71 CASES

A multicenter study of 71 aneurysmal bone cysts (ABCs) including eight in the spine and 63 in appendicular bones is reported. These 71 cases contributed 16% of the 435 benign bone tumors identified during a nat ion-wide multicenter study, versus 1.5 to 4% in previous studies in va rious countries, Seventy-four per cent of patients were younger than 2 0 years; 25% were younger than ten years, and 49% were aged ten to 20 years, Presenting problems and clinical symptoms varied with the locat ion of the ABC. Neurologic complications occurred in as many as 75% of patients with spinal ABCs. Sixty-five per cent of patients with appen dicular ABCs presented with a bone mass that had developed slowly over several months or years with or without pain or other symptoms, and 2 5% presented with a pathological fracture. Pathological studies were e ssential to the diagnosis. The typical pattern was a multiloculated cy stic cavity filled with hemolyzed blood and bounded by osteofibrous wa lls, Cells in the walls included fibroblasts, multinucleate giant cell s, histiocytes, and siderophages. Immunohistochemical studies demonstr ated that the cavities were not lined by endothelium and were therefor e not vascular in nature. Two cases coexisted with osteosarcoma.