Periosteal Osteosarcoma

Comments:
Most cases of periosteal osteosarcoma are moderately-differentiated chondroblastic type. The tumor shows lobules of cartilaginous matrix with condensation and spindling of tumor cells at the periphery of the lobules. Bony trabeculae may be seen in the center of the lobules. A high-grade (Grade IV) pleomorphic tumor is incompatible with the diagnosis of periosteal osteosarcoma.