Immunohistochemical expression of internal and external ErbB-2 domains in invasive breast cancer

We tested three ErbB-2 monoclonal antibodies (MoAbs) specific to the intrac ytoplasmic internal domain (clone CB 11) and the extracellular glycosylated peptide domain (clones CBE1 and Tab250) in 351 primary invasive breast car cinomas. ErbB-2 immunodetection allowed us to differentiate three main grou ps: group 1 (62.7%) lacked both MoAb ErbB-2 domains (erb -/-); group 2 stai ned for both domains (erb +/+) (26.5%); group 3 stained for the internal do main only (erb +/-) (10.8%). The relationships among these groups and nodal status (N) were statistically significant, with N+ cases reaching the high est value (89.2%) in the erb +/- group. Lack of immunostaining in the exter nal domain thus seems to be associated with increased metastatic spread. At variance analysis the difference in hormonal receptor content between grou ps 1 and 3 was not significant; while between groups 1 and 2 it was. The gr owth fraction of groups 2 and 3 was significantly higher than that of group 1. Our results showed that anti-ErbB-2 MoAb clone CB 11 was able to detect a higher number of ErbB-2 expressing cases than the two that are specific for the external domain (clones Tab 250 and CBE1). Due to the strong associ ation between group 3 cases and the highest metastatic potential, this aggr essive group could be identified only with the use of an internal-domain sp ecific MoAb CB11, which thus seems to present a better discriminative power as a diagnostic marker in the biopathological characterization of breast c arcinoma.