Immunohistochemical Study on Overexpression of c‐erbB‐2 Protein in Human Breast Cancer: Its Correlation with Gene Amplification and Long‐term Survival of Patients

Using a polyclonal antibody monospecific to the c-erbB-2 oncogene product, an immunohistochemical study on the expression of c-erbB-2 protein was performed in formalin-fixed, paraffin-embedded tissue sections from 176 primary breast carcinomas in which amplification of the c-erbB-2 gene had been detected in 28 cases. Expression of the c-erbB-2 protein was detected in 44 cases (25%), being strongly positive in 27 (15%) and weakly positive in 17 (10%). All cases with amplification of c-erbB-2 showed positive staining of its protein. There were only four cases in which c-erbB-2 was strongly expressed without amplification of the gene. In the group showing strongly positive staining, both overall and disease-free survival were significantly poorer than in the remainder of the cases. Using Cox's regression model analysis, overexpression of c-erbB-2 protein was demonstrated to be an effective prognostic factor independent of nodal status or tumor size.