Fig. 6

Left ilium tumor removal operation. a Infiltrative tumor borders, incomplete “bone shell”-like structures around the tumor (Haematoxylin and Eosin stained, original magnification× 100). b The tumor cell is oval, spindle, or star-shaped, has a small nucleus and nucleolus, has increased density, and has a fibrous histiocytoma-like structure (Haematoxylin and Eosin stained, original magnification× 200). c A small amount of ossifying fibroma-like areas can still be seen in recurrent tumors, the cell density is increased, the cells are mild to moderately atypia, and mitosis is easily seen (Haematoxylin and Eosin stained, original magnification× 200). d Tumor infiltration destroys the surrounding host bones and smoke-like calcification is not obvious (Haematoxylin and Eosin stained, original magnification× 200). e Occasionally smoked calcifications (blue arrows) and scattered osteoclast-like giant cells (red arrows) are seen in recurrent tumors (Haematoxylin and Eosin stained, original magnification× 200). f The mitotic figures (red arrow) have more than 5/10 HPF and moderate dysplasia is seen (Haematoxylin and Eosin stained, original magnification× 400)