Periosteal chondrosarcoma and periosteal osteosarcoma. Two distinct entities.

This review of 27 cases serves to emphasis that periosteal chondrosarcoma and periosteal osteosarcoma are two distinct entities. Clinically, periosteal chondrosarcoma is less painful than periosteal osteosarcoma and runs a slower course. Radiographically, periosteal chondrosarcoma tends to affect the metaphysis and contains granular or "popcorn" opacities; while periosteal osteosarcoma more often affects the mid-diaphysis and shows lytic lesions with some spicules of reactive bone perpendicular to the underlying cortex. Histologically, periosteal chondrosarcoma shows lobular well-differentiated cartilage with Grade I or II (rarely Grade III) malignancy; periosteal osteosarcoma has a chondroid matrix with some osteoid component and Grade II or III malignancy. The prognosis in periosteal chondrosarcoma is good; conservative surgery is usually effective and metastases are very uncommon. In periosteal osteosarcoma the prognosis is less satisfactory but is better than that of other osteosarcomata; wide surgical excision is, however, needed and the incidence of metastases is about 15 per cent.