Histopathology examination by hematoxylin and eosin stain (H&E). (a) Tumor is composed of spaces separated by septa (blood-filled cavities) (H&E; 4x). (b) Spindle cell proliferation with classification and osteoid formation (H&E; 10x). (c) Cellular components with osteoclast-like giant cells (H&E; 40x). (d) Numerous mitotic figures are seen (arrow head) (H&E; 40x).