EGFR expression stratifies oligodendroglioma behavior.

Epidermal growth factor receptor (EGFR) expression and signaling contribute to glioma biological features and, thus, are a target for new drug development. The role, if any, of EGFR in routine surgical neuropathological diagnostics is less clear. Herein, we describe prospective EGFR IHC analysis in an adult cohort comprising 750 infiltrative gliomas. EGFR expression increased with World Health Organization grade but did not significantly differ between grade-matched astrocytic and oligodendroglial tumors. Survival did not significantly differ by EGFR expression among astrocytic tumors adjusted for World Health Organization grade. However, grade II oligodendrogliomas with strong EGFR expression and 1p/19q codeletion showed reduced survival, compared with their codeleted counterparts with weaker EGFR expression. Surprisingly, an inverse phenomenon was found with grade III anaplastic oligodendrogliomas, in which stronger EGFR expression was a favorable marker for survival. Among all gliomas, the likelihood of EGFR amplification, as viewed by fluorescence in situ hybridization, increased with the strength of EGFR expression, and <1% of cases with weak or no EGFR immunostaining showed amplification. These data suggest that EGFR IHC is useful in certain circumstances (ie, it may help supplement 1p/19q prognostic information in oligodendroglial tumors and screen out cases that would not benefit from more costly EGFR fluorescence in situ hybridization analysis).