Giant-cell tumor of bone should be differentiated from all other lesions which also contain multinuclear giant cells, including solitary bone cyst, non-osteogenic fibroma, aneurysmal bone cyst, chondromyxoid fibroma of bone, benign chondroblastoma, and the "brown tumors" sometimes found in hyperparathyroidism. The giant-cell tumor of bone is clinically, anatomically, and cytologically a distinctive neoplasm. The pathologist who depends entirely upon the microscopic examination and ignores the clinical history and roentgenographic examination will make many errors of diagnosis. Irradiation as a primary or total plan of treatment of giant-cell tumors of bone is neither certain of cure nor free from danger. The larger giant-cell tumors cannot be destroyed by irradiation without severe damage to adjacent tissues. Most giant-cell tumors may be adequately and safely treated by surgery, followed in some instances by irradiation therapy.5, 8, 12, 13