Histologic grading of Wilms' tumor as potential prognostic factor: results of a retrospective study of 26 patients

A histologic grading system based on tumor differentiation was applied in a retrospective study of 26 patients with Wilms' tumor to determine if it might provide an index to prognosis. The results were compared to those obtained by applying a histologic classification based on the presence or absence of individual histologic structures to the same tumors. Low grade tumors with predominance of differentiated structures--glomeruli and tubules--were associated with a better cure rate than high grade tumors composed mainly of undifferentiated spindle elements. The presence of undifferentiated large cells correlated with poor cure rate. The findings suggest that histologic grading may be valid as a prognostic factor in Wilms' tumor.