Staging of musculoskeletal tumors

There are three major staging systems for bone and soft tissue tumors. These are based on the histologic grade of the tumor and its anatomic site, as well as the presence or absence of any involved nodes, skip lesions, or metastases. With a few notable exceptions, however, radiologists do not seem to be aware of these staging systems, clinicians do not seem to be using them, and the literature on the subject is sparse. Another facet has also presented itself with the advent of MR imaging that allows us to see findings that were not readily visible before. For instance, some large homogeneous tumors appear to have a pseudocapsule (Fig. 4), but although this is almost certainly a phase shift artifact, there presumably must be a cleavage plane between the tumor and the underlying tissues at this interface. What role will this finding play in the staging of the tumor? Some tumors are associated with the presence of fluid running up and around fascial planes high above the level of the tumor itself (Fig. 5). How will this affect the stage of the lesion? We think that once enough experience has been gained with the interpretation of these MR images, a new and more comprehensive staging system will have to be introduced.