Malignant Transformation of Giant Cell Tumor of Bone 7 years After Initial Surgery: A Case Report and Literature Review.

CASE A 64-year-old man with a history of giant cell tumor of bone (GCTB) in the fibula 7 years earlier developed a recurrence with histologic features of osteosarcoma. Both the primary GCTB and the secondary osteosarcoma were found to have the H3F3A gene mutation. Despite immediate above-the-knee amputation, the patient died of respiratory failure because of lung metastases 3 months later. CONCLUSION This is the first report of proven H3F3A mutation in both the primary GCTB and the secondary osteosarcoma in the same case. Clinicians should consider secondary malignancy in patients presenting with a lesion at the site of a previously treated GCTB after a long interval.