ERBB4 and breast carcinoma: A study of 130 breast carcinomas did yield more 2+ and 3+ cases when using the PATHWAY® HER2 antibody than when employing the HercepTestTM antibody, although a very high concordance between PATHWAY® HER2 IHC and fluorescence in-situ hybridization (FISH) was found.13 Conversely, if HER4 is expressed mainly together with high levels of HER2, the simultaneous detection of both proteins would have no clinical implications in the assignment or not of HER2-targeted therapy.