c-erB-2 oncoprotein expression in malignant and nonmalignant breast tissue.

Using a specific polyclonal antibody (21N) to the c-erbB-2 oncoprotein, a total of 200 primary breast carcinomas of various histological types and 46 benign breast lesions, were immunohistochemically stained, to identify those tissues over-expressing this putative transmembrane receptor. Positivity for this oncoprotein was evident as an intense brown granular staining predominantly located at the cell membrane and was present in 17% (n = 34) of the primary breast carcinomas investigated. With the exception of one case of apocrine metaplasia, none of the remaining benign breast samples (n = 45) were positive for this oncoprotein. This study shows that overexpression of the c-erb B-2 oncoprotein is easily identifiable and can be detected on paraffin embedded sections using an immunohistochemical technique. The results obtained correlate well with other c-erbB2 detection systems and in addition, positivity for this oncoprotein is mostly confined to the malignant phenotype.