p53 expression in gastrointestinal stromal tumors.

The understanding of gastrointestinal stromal tumors (GIST) is complex because of their divergent differentiation and unpredictable behavior. However, our understanding is becoming clearer, despite some cases of tumors which are exceptions from the typical cases. Tumor size, mitotic rate and, to a lesser degree, location, are the most important predictive parameters for the behavior of GIST. In this study, expression of p53 protein was evaluated in 15 cases of GIST. Tumors were divided into three groups: (i) benign (mitotic index [MI] < 5/50 high-power fields [HPF] and size < 5 cm); (ii) borderline (MI < 5/50 HPF and size > or = 5 cm); and (iii) malignant (MI > or = 5/50 HPF, irrespective of size). The mean values of p53 expression in the three groups were significantly different (benign, 10.6%; borderline, 33.8%; and malignant, 71%). The conclusion of the present study is that p53 overexpression correlates well with the malignant potential of GIST.