C-ERBB-3 AND C-ERBB-2 PROTEIN EXPRESSION IN NODE-NEGATIVE BREAST-CARCINOMA - AN IMMUNOCYTOCHEMICAL STUDY

The type I growth factor receptor family has been found to play an imp ortant role in the control of normal growth and differentiation. Moreo ver, the epidermal growth factor receptor and the c-erbB-2 oncogene se em to be implicated in the pathogenesis and behaviour of several cance rs, including breast cancer. c-erbB-3 is a new member of the type I re ceptor family for which there is currently little information availabl e on its expression in neoplastic tissues, and on its possible prognos tic significance. This study was undertaken to define the prognostic v alue of c-erbB-3 expression in a series of node-negative breast cancer (NNBC) patients when compared, by multivariate analysis, with express ion of the c-erbB-2 protein and conventional clinicopathological featu res. cerbB-3 was recognised by the novel monoclonal antibody RTJ1, whe reas c-erbB-2 was detected by the polyclonal antibody 21N, using immun ocytochemical methods. We found that overexpression of c-erbB-3 occurs frequently in NNBC. Overall, 138 of 212 carcinomas (65%) had some deg ree of membrane RTJ1 staining, and 28 (13%) showed strong and generali sed positivity (+++). Twenty-four per cent of carcinomas had membrane 21N staining, and 12% presented strong and generalised positivity (++). c-erbB-3 protein expression was significantly associated only with that of c-erbB-2 (P = 0.05), whereas 21N positivity was significantly associated with small tumour size (P = 0.02) and ductal histotype (P = 0.04). No significant correlation between expression of either recept or proteins or relapse-free survival was observed after a median follo w-up of 63 months. Applying multivariate analysis, only tumour size ap proached significance. Our results indicate that analysis of expressio n of c-erbB-3 and c-erbB-2 alone do not seem to be useful in identifyi ng patients with NNBC at different risk of relapse or death.