EGFR gene and protein expression in breast cancers

Aims To measure the EGFR gene amplification and protein expression, and to compare the EGFR expression with HER2 expression similarly measured. Methods EGFR gene amplification was assayed by fluorescence in situ hybridization and its protein expression was evaluated by immunohistochemistry on tissue microarray of 165 consecutive invasive breast cancers. Results EGFR protein overexpression was observed in 20.6% of the 165 studied cases, but gene amplification was observed in 7.9% only. EGFR protein was expressed in 33.3% of HER2-amplified tumors, and in only 16.3% of HER2 non-amplified tumors. EGFR expression significantly increased in HER2 gene-amplified and protein-expressing tumors as well. On survival analysis, EGFR expression was a significant prognostic factor for the disease-free and overall survival of the patients. Conclusions EGFR protein expression was independent of EGFR gene amplification status, whereas it was intimately associated with HER2 amplification and overexpression in breast cancer.