Principles of staging of soft-tissue sarcomas.

The TNM staging system is a modus for diagnosis and treatment in which T is the extent of the tumor involvement, N is lymph node involvement, and M is the metastases; this system is supplemented with a histologic malignancy grade. Staging systems identify specific prognostic factors with which to predict clinical outcome. Staging systems are useful for assigning treatment priorities, determining the role of adjuvant therapies, and evaluating clinical investigations. Unfortunately, no universally accepted staging system for soft-tissue sarcomas exists. This is related to the relatively low incidence of sarcomas, the unique and unpredictable behavior of sarcomas, significant disagreement regarding histogenesis and grading, and lack of consensus regarding the value of various prognostic factors. In adults, the two most commonly used staging systems are those developed by the American Joint Committee on Cancer and by Enneking. In children, the Intergroup Rhabdomyosarcoma Study and the International Union Against Cancer have described the systems most commonly used. These systems for soft-tissue sarcomas rely on an ability to accurately determine both the local and distant extent of disease. Advances in the field of computed tomography and magnetic resonance imaging have made this possible. It is likely that a staging system based upon a more sophisticated understanding of the basic biology of sarcomas will become available.