Grading of soft tissue sarcomas: experience of the EORTC Soft Tissue and Bone Sarcoma Group.

A practical grading system for soft tissue sarcomas was developed, based on 282 eligible patients entered in an EORTC adjuvant clinical trial. The primary tumours in this trial had to be adequately treated. Histopathological parameters, which appeared significant in two preceding studies, were tested. These parameters were differentiation of the tumour, presence and amount of necrosis, the presence and amount of myxoid areas and the number of mitoses. In addition, the size of the tumour was also analysed. The quantitative data (mitotic count and size of the tumour) were not a priori grouped, but were divided into categories based on the results of the statistical analysis. Based on a multivariate analysis only mitotic count, the presence or absence of necrosis and the size of the tumour were significantly correlated with the duration of survival or the time to distant metastases. Of these parameters, the mitotic count was the most important.