The role of immunohistochemistry in predicting behavior of astrocytic tumors.

The purpose of this study was to analyze the significance of p53, bcl-2 and EGFR expression in the grading and biological behavior of astrocytic tumors, especially in the Indian population. A total of 117 cases of astrocytomas graded using the WHO grading system published in 2007 were immunolabeled using p53, EGFR and bcl-2 monoclonal antibodies and analyzed with respect to grade and other relevant parameters. The 117 cases included 16 cases of pilocytic astrocytomas and 25, 15 and 61 cases of diffuse fibrillary astrocytomas WHO grade II, anaplastic astrocytomas WHO grade III and glioblastomas (GBM), respectively. Our results showed that p53 alterations is an early event in astrocytic gliomagenesis, but is not significant in the evolution of pilocytic astrocytomas. Bcl-2 expression did not correlate with grade and no statistical correlation was seen with p53 expression. EGFR protein expression correlated with the severity of tumor grade. Of the GBM cases, 47.5% were p53 positive only, 18% were EGFR positive only, 16.5% were negative for both and 18% were positive for both. The mean age in the dual positive category was significantly higher when compared to the others. EGFR and p53 alterations are not mutually exclusive and might act synergistically to promote progression. We also noted a significantly higher p53 expression in females in GBMs. Though most of our findings correlated with those of previous studies, some differences were noted, especially in the pattern of immunoexpression in GBMs, perhaps because of ethnicity.