fig4

Figure 4. CT scan image of periosteal osteosarcoma originating in tibial diaphysis, forming bone, with thick periosteal bone formation. The neoplasm is elongated, mainly lucent (A); Subperiosteal, fusiform mass with broad base of attachment to outer cortex of host bone. The external surface is covered by fibrous tissue. The cut surface is mostly cartilaginous, but also contains perpendicular bands of ossification (B); Chondroblastic lobules separated by bands of undifferentiated spindle cells (H&E; 25X) (C); Osteoid-producing undifferentiated neoplastic cells (H&E, 50X) (D)