Relationship between EGFR overexpression and gene amplification status in central nervous system gliomas

OBJECTIVE: To correlate epidermal growth factor receptor (EGFR) protein overexpression, as assessed by immunohistochemistry, with EGFR gene amplification determined by fluorescence in situ hybridization in a series of gliomas. STUDY DESIGN: Forty-seven central nervous system gliomas, including 34 cases of glioblastoma multiforme, 3 oligodendrogliomas, 4 juvenile pilocytic astrocytomas and 5 low grade astrocytomas, were obtained from the files of the University of Utah Pathology Department. In each case a representative paraffin block was selected, and EGFR protein expression was quantified using immunohistochemistry. EGFR gene amplification status was determined by fluorescence in situ hybridization. RESULTS: EGFR protein overexpression was detected in 9 cases of glioblastoma multiforme. EGFR gene amplification was present in 7 of these cases. Both nonamplified glioblastomas demonstrated only 2+ overexpression of EGFR protein. None of the low grade, pilocytic or anaplastic astrocytomas demonstrated either EGFR protein overexpression or gene amplification. CONCLUSION: EGFR protein overexpression is closely associated with gene amplification. Seventy-eight percent of cases showing protein overexpression demonstrated gene amplification. All cases of central nervous system neoplasms showing protein overexpression but lacking gene amplification were associated with only 2+ protein overexpression. All central nervous system neoplasms demonstrating gene amplification and/or overexpression were high grade neoplasms.