Grading in soft tissue tumors: principles and problems

Histologic grading has been considered the most important prognostic factor for soft tissue sarcomas. Several grading systems have been proposed based on the assessment of morphologic features in heterogeneous groups of sarco mas. Currently, the French Federation of Cancer Centers (FNCLCC) and the Na tional Cancer Institute (NCI) grading systems are the most commonly used. T hese systems are based on a few morphologic predictors of biologic behavior , which is justifiable because of the rarity of soft tissue sarcomas. Nonet heless, over- or underestimation of prognosis may occur because of an uneve n representation of specific sarcomas with rather distinct biologic behavio rs among studies of grading systems. In addition, lack of standardization o f morphologic criteria and frequent omission of the influence of clinical f actors on the final survival analyses preclude universal acceptance of a pa rticular grading system. New advances in diagnostic imaging, quantitative m orphometric technologies, cytogenetics, and molecular genetics, allied with alternative analytic data systems, may provide better validation, reproduc ibility, and prognostic capabilities for current and future grading systems . This article summarizes and critically analyzes the various important gra ding systems that have thus far been proposed and suggests alternatives for the elaboration of more reproducible systems with higher predictive capabi lities.