The histopathological grading of soft tissue tumours: current concepts

Abstract

Malignant tumours of soft tissue (sarcomas) represent a heterogeneous group of neoplasms which differ widely in their potential clinico-biological behaviour, ranging from lesions with an indolent clinical course to lesions that behave in a highly aggressive manner. While certain tumours exhibit fairly consistent and predictable histotype-specific behaviour (underscoring the importance of accurate histopathological classification), other lesions have a broad range of clinical behaviour not immediately predictable from histological typing alone. Due to the relative rarity of malignant soft tissue tumours, studying and comparing large groups of individual tumour types is problematic. Consequently, the identification of histotype-specific parameters that may influence and/or predict clinical behaviour remains difficult, limiting knowledge about possible prognostic parameters for many of the rarer sarcomas. Histopathological grading of sarcomas as a general group represents an attempt to identify histotype-independent histological parameters that may be of use in predicting prognosis. Specifically, this is primarily applicable to those tumour types which exhibit a broad range of biological behaviour, newer tumour entities with an as yet uncertain longer term clinical course, unclassifiable lesions, and lesions about which there is diagnostic disagreement. Histopathological grading has direct clinical application in the design of prospective clinical trials to compare the clinical outcome of various management protocols and hence select optimal treatment strategies. The two best established and most widely used grading schemes are the ‘National Cancer Institute’ and the ‘Fédération Nationale des Centres de Lutte Contre le Cancer’ systems. Despite its limitations, histopathological grading appears to be effective in predicting distant metastasis as well as overall survival. Recent studies are beginning to indicate that genetic variability within certain tumour groups may be of prognostic value, potentially facilitating efforts at prognostication for certain tumour types/subtypes.