Immunohistochemical expression and significance of epidermal growth factor receptor (EGFR) in breast cancer.

Breast cancer is a heterogeneous disease that includes several molecular types, characterized by the expression profile of sex hormone receptors, HER2 protein, cytokeratin 5, p53, and Bcl-2. EGFR is an additional marker predominantly expressed by basal-like carcinoma, but its significance in the other types is not completely understood. The aim of this study was to analyze the immunohistochemical expression of EGFR and its relationships with other factors of prognosis. There were investigated benign lesions and 84 cases with invasive breast carcinoma that were submitted first to the molecular classification. Next, we performed the staining for EGFR and two patterns of the final product of reaction were described. EGFR expression was found in 41.66% of the cases with basal-like carcinoma, in 50% of the cases with luminal B carcinoma, and in 21.42% of the cases with HER2 overexpression. A significant correlation was found between EGFR expression and degree of differentiation and distant metastasis. No significant correlation was found with the lymph node status, excepting for the basal-like carcinoma in which an inverse correlation was noticed. Our results suggest that EGFR expression by tumor cells of the breast cancer defines a specific subset of tumors with poor prognosis and potential resistance to the adjuvant therapy.