c-erbB-2 in astrocytomas: infrequent overexpression by immunohistochemistry and absence of gene amplification by fluorescence in situ hybridization.

Recent studies suggest that aberrations of c-erbB-2 may be involved in astrocytic brain tumours. We screened immunohistochemically c-erbB2 protein (p185) expression in 94 astrocytic grade 1-4 neoplasms of the brain. The amplification of the c-erbB-2 oncogene was investigated in protein overexpression cases by dual colour fluorescence in situ hybridisation (FISH). p185 overexpression was correlated with p53 and epidermal growth factor receptor (EGFR) expression, as well as with clinicopathological features. Only two anaplastic (grade 3) astrocytomas and one glioblastoma (grade 4) showed overexpression of p185 protein by immunohistochemistry (monoclonal MAb1 antibody TA250), whereas none of the grade 1-2 astrocytomas was positive. Interestingly, the expression of p185 was confined solely to the cytoplasm of neoplastic astrocytic cells and not to the cell membranes as found in malignancies with amplification of the c-erbB-2 oncogene. Two of the three overexpression cases were also positive by EGFR. No amplification of the c-erbB-2 gene was observed by FISH in the three tumours with immunohistochemical p185 overexpression or seven weakly positive/negative tumours. In conclusion, our results suggest that p185 overexpression is infrequent in astrocytomas, that it is of no important diagnostic or prognostic value and that c-erbB-2 oncogene amplification is not seen in the few cases in which there is overexpression.