Clinical and radiological features of atypical giant cell tumours of bone.

Giant cell tumour (GCT) of bone is an uncommon neoplasm, representing approximately 5% of all bone neoplasms and approximately 21% of benign bone tumours (Dahlin & Unni, 1986). The vast majority of GCTs arise after closure of the growth plate and occur at the end of long bones. GCTs are frequently diagnosed by radiologists because of their preferred location (80% in long bones of the extremities), age distribution (peak incidence in the third decade) and morphologic appearance. Typically, they are expanding radiolucent lesions eccentrically located, most commonly at the articular surface of a long bone. Pathologic and histologic findings are characteristic, although these tumours need to be differentiated from other lesions containing giant cells, such as non-ossifying fibroma, aneurysmal bone cyst, osteoblastoma, chondroblastoma, giant cell reparative granuloma, benign fibrous histiocytoma and brown tumours. The biologic behaviour of GCT frequently is not predictable. In our experience, shared by most au...