Malignant transformation of a giant cell tumor 25 years after initial treatment.

The current authors report a patient in whom a malignant fibrous histiocytoma developed long after a benign giant cell tumor of bone was removed from the same site. Twenty-five years after a benign giant cell tumor of the lateral condyle of the proximal tibia had been treated by curettage and iliac bone grafting without radiotherapy, a 53-year-old woman noted progressive pain and an enlarging mass in the same area. Radiographs showed osteolytic change, whereas magnetic resonance imaging indicated a tumor arising at the site of the giant cell tumor and extending beyond the bone. Examination of an open biopsy specimen showed a high-grade malignant fibrous histiocytoma with some areas rich in giant cells. After five courses of caffeine assisted intraarterial chemotherapy, the tumor was resected with an adequate margin, and the defect was reconstructed with an implanted prosthesis of corresponding shape. The extensor mechanism of the knee was reinforced using an allograft of fascia from the tensor fascia lata muscle. The resected specimen showed a good histologic response (95% tumor necrosis) to preoperative chemotherapy. Excellent function in the knee has been regained with no evidence of disease recurrence. Caffeine potentiated chemotherapy was effective in minimizing the extent of tumor excision, in this case of high-grade malignant fibrous histiocytoma representing transformation from a benign giant cell tumor.