Epidermal growth factor receptor overexpression is common and not correlated to gene copy number in ependymoma

PURPOSE: The aim of this study was to investigate the epidermal growth factor receptor (EGFR) status in ependymoma specimens, as there is a need for new prognostic and druggable targets in this disease.

METHODS: Ependymomas (WHO grade II, n = 40; WHO grade III, n = 15) located spinal (n = 35), infratentorial (n = 14), and supratentorial (n = 6) of 53 patients with a median age of 40 (range, 2-79) years were analyzed for Ki-67, p53, and EGFR expression by immunohistochemistry using a tissue microarray and for EGFR gene copy number alterations/mutations. Results were correlated to clinical data.

RESULTS: EGFR overexpression was found in 30/60 % of ependymomas depending on the antibody used and was more pronounced in WHO grade III. High EGFR gene copy number gains were found in 6 (11 %) ependymomas with half of them being amplifications. EGFR amplified ependymomas displayed an EGFR overexpression with both antibodies in two of three cases. A missense mutation in exon 20 of EGFR (S768I) was detected in one amplified case.

CONCLUSIONS: EGFR is frequently overexpressed in ependymomas. Other mechanisms than amplification of the EGFR gene appear to contribute to EGFR overexpression in most cases. EGFR mutations may be present in a small subset of ependymomas.