Osteoblastoma-like osteosarcoma: High-grade or low-grade osteosarcoma?

Osteoblastoma-like osteosarcoma is a rare variant of osteosarcoma (1% of all osteosarcomas), histologically similar to osteoblastoma. In the current WHO classification osteoblastoma-like osteosarcoma is classified within the group of conventional (high-grade) osteosarcomas. However, several published cases have been actually regarded as low-grade malignant tumors. Since strict morphologic criteria to distinguish between low-grade and high-grade lesions are not available we reviewed our series of osteoblastoma-like osteosarcomas in the attempt to identify clinical and morphologic features predictive of aggressiveness.