Fig. 4

Histopathological findings. a Hematoxylin and eosin staining (×400): neither tumor osteoid formation nor residual areas of giant cell tumors of bone are present. There is dense proliferation of tumor cells with atypia/nuclear division. Undifferentiated pleomorphic sarcoma transformation was diagnosed. b Tumor necrosis factor-α staining (×400): the tumor specimen expressed tumor necrosis factor-α. HE hematoxylin and eosin, TNF-α tumor necrosis factor-α.