Differential expression of estrogen, progesterone, and epidermal growth factor receptors in normal, benign, and malignant human breast tissues using dual staining immunohistochemistry.

Distribution of estrogen (ER), progesterone (PR) receptors, and epidermal growth factor (EGF) receptors was assayed by dual staining immunohistochemistry on 28 selected cytosolic ER-positive breast carcinomas and 22 nonmalignant breast tissues. ER-positive tumor cells were detected in 26 (93%) and EGF receptor positive tumor cells were detected in 7 (25%) carcinomas. In five tumors both ER and EGF receptors were detected but localized in distinct tumor cells. Only in one case of ductal carcinoma in situ co-expression was observed in a subset of tumor cells. In contrast, simultaneous expression of ER/PR and EGF receptors was observed in non-neoplastic ductal remnants in the majority of the carcinomas and the fibroadenomas. In addition, double-positive cells were occasionally detected in luminal epithelial cells of normal breast tissue and mastopathies. This study shows that ER/PR and EGF receptors in breast tumor cells are inversely related at the single cell level. However, demonstration of ER/PR and EGF receptors in individual normal luminal cells shows that expression is not mutually exclusive.