p53 abnormality and tumor invasion in patients with malignant astrocytoma.

Malignant astrocytomas are characterized by diffusely infiltrating nature, and the abnormality of p53 is a cytogenetic hallmark of astrocytic tumors. To elucidate the relationship between p53 abnormality and invasiveness of the tumors, we studied mutation and protein expression of p53 in 48 consecutive patients with malignant astrocytoma (14 anaplastic astrocytomas and 34 glioblastoma multiformes). The tumors were classified into three categories according to the features of magnetic resonance imaging, and 5, 7, and 36 tumors were classified into diffuse, multiple, and single type, respectively. We then examined how these tumor types correlate with MIB-1 staining index, TP53 gene mutation, and p53 protein expression. We found that p53 immunopositivity or TP53 mutation was frequently observed in diffuse and multiple types. These abnormalities of p53 were also associated with high MIB-1 staining index and strong expression of vascular endothelial growth factor. Furthermore, diffuse- and multiple-type tumors were significantly correlated with poor progression-free survival, whereas only multiple-type tumors were significantly correlated with poor overall survival. As diffuse and multiple features on imaging modalities represent invasive characteristics of the tumors, p53 abnormalities may affect the invasive and aggressive nature of malignant astrocytomas.