Immunocytochemical and biochemical analysis of epidermal growth factor receptor expression in human breast cancer tissues: Relationship to estrogen receptor and lymphatic invasion

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Abstract
Expression of epidermal growth factor receptor (EGFR) and estrogen receptor (ER) was examined by an immunocytochemical assay (ICA) using serial cross‐sections of human breast cancer tissues. Immunocytochemical results were compared with those obtained by biochemical competitive binding assay and with histological lymphatic invasion. EGFR was evaluated as positive in 17 (34.0%) out of 50 primary tumors by ICA. A significant inverse relationship of the proportion of stained cells between EGFR and ER was demonstrated. In more than one‐half of the tumors that were positive for both EGFR and ER, these 2 receptors were inversely stained in relation to the distribution. In ER‐negative cells, EGFR expression was more marked than in ER‐positive cells. Biochemical data confirmed the immunocytochemical results, pointing to an inverse relationship between EGFR and ER content. EGFR status correlated well with the degree of lymphatic invasion but not with the number of lymph nodes with metastases.