[A histological study on osteosarcoma. Part II: The mode of local extension of osteosarcoma].

The survival rate of patient with osteosarcoma has been increasing, owing to the development of adjuvant chemotherapy. Recently, the limb saving procedure in osteosarcoma has been attempted in many countries. Although we need knowledge about the mode of local extension of osteosarcoma in the planning of this surgery, there are few reports concerning the matter. The purpose of this paper is to make clear, morphologically, how tumor tissue extends across the epiphyseal plate, periosteum and bone marrow. The materials were 26 amputated extremities of osteosarcoma which had not received any chemotherapy or radiotherapy. Paraffin embedded macrosections were prepared and stained with HE and Masson stain. When epiphyseal plate was open or closing, 13 out of 14 cases (93%) showed transphyseal extension of tumor. Tumor extension along the vessels at the center of the plate and the epiphyseal artery was most common. Transmedullary extension showed three different types, infiltrative type (18 cases), lobular type (5 cases), and "skip" type (one case). None had capsule or pseudocapsule surrounding the tumor. As to the relationship between periosteal reaction and tumor involvement of cortex or medulla, periosteal reaction was located more proximally than cortical or medullary involvement in some cases. In other cases, however, cortical or medullary involvement was located more proximally than periosteal reaction. The gaps between the tips of the periosteal reaction and cortical or medullary involvement ranged from 0.5 to 1.5 cm. In the transperiosteal extension, it was confirmed that tumor cells had invaded the periosteum along the vessels penetrating the periosteum.