Pulmonary metastases from a well differentiated giant cell tumor of bone. Report of a patient with apparent response to cyclophosphamide therapy

The biologic behavior of giant cell tumors of bone cannot always be predicted from histologic appearance alone. In this case report, a histologically 'benign' giant cell tumor of the tibia metastasized to the lung, but over the course of 5 yr, exhibited little change in its well differentiated histologic appearance. Electron microscopy revealed ultrastructural features similar to those reported in clinically nonaggressive giant cell tumors. Control of pulmonary symptoms (pleuritic pain, hemoptysis) and stabilization of tumor growth followed the use of high dose cyclophosphamide. Although maintainance of a well differentiated appearace in the face of proven metastases is rare for this type of tumor, a number of similar examples have been recorded in the literature. As a rule, these patients enjoy a relatively favorable prognosis, when compared with those individuals in whom the metastases exhibit obvious sarcomatous dedifferentiation.