[Pathologic and radiologic study of parosteal osteosarcoma. Report of 17 cases]

17 cases of parosteal osteosarcoma (POS) were studied radiologically and pathologically. It was found that the differentiation of the tumor component in the narrow basic area was the poorest and the surrounding part was the next. The tumor has the tendency to invade the cortex and then infiltrate the surrounding soft tissues in the early stage of tumor formation at the narrow basic area. We have summed up four types of essential X-ray features of cortical erosion and their pathological bases, clarified the limited ability of X-ray to reveal early cortical invasion and the range of infiltration. It seems that POS has the tendency of dedifferentiation on the whole, not being limited in one subtype.