Prognostic factors in malignant gastrointestinal stromal tumors.

Gastrointestinal stromal tumors are a heterogeneous group of mesenchymal neoplasms of the gastrointestinal tract in which routine histopathological evaluation fails to reveal definitive evidence of differentiation. Given the heterogeneity in clinical presentation and the frequent morphological overlap, the biological behavior of these neoplasms is difficult to predict. We have evaluated, by Cox Proportional Hazards Regression Analysis, the clinicopathological features of 51 malignant gastrointestinal stromal tumors to identify predictors of survival. In the univariate analysis, survival inversely correlated with size, number of mitoses, and patient's age. In the multivariate analysis, only the degree of necrosis and phenotypic differentiation toward smooth muscle were found to be indicators of poor prognosis. Based on these results, a simple classification scheme for gastrointestinal stromal tumors is proposed. This classification appears to have great prognostic value for these tumors, and may be useful in guiding therapeutic management.