Giant cell tumor of bone with late-onset lung metastasis and secondary osteosarcomatous transformation

This case report presents a rare occurrence of a primary giant cell tumor (GCT) of bone with subsequent metastasis to the lung, undergoing osteosarcomatous transformation, with a significant temporal gap of 10 years between the two tumor events. A 32-year-old male initially presented with a primary GCT of the distal femur, which was treated with curettage and adjuvant therapy. Ten years later, he developed pulmonary metastasis, exhibiting features of an osteosarcomatous transformation of the previously diagnosed GCT. This case underscores the importance of long-term surveillance in patients with GCTs and the potential for malignant transformation over time.