RESUMO
Secondary malignant giant cell tumour of bone occurs as a result of previous attempts at local control of a benign giant cell tumour of bone (GCT). Out of the total 445 conventional benign GCT of bone, therapeutic irradiation was given in 39 cases as the lesions were located in the vertebrae and pelvic bones where debulking surgery was not possible and the tumours were pressing on the spinal cord. The patients were followed up for 21 years. Out of 39 cases, 5 patients developed sarcomas of which 3 were fibrosarcomas, 1 was malignant fibrous histiocytoma while 1 was an osteosarcoma. All the patients developing post-radiation sarcomas died within a few months due to lung metastasis. In conclusion, all the patients with benign GCT of bone treated with radiation must be followed life long as they are prone to develop sarcomas.