ERBB3 and breast cancer: These data, including the frequency of marker expression, are concordant with our findings for ERBB2 and especially EGFR. Besides the presence and persistence of a variety of genes in that BC subtype, probably leading to worse outcome, we were further able to show that EGFR+/ERBB2+/ERBB3 + CTCs BT as well as ERBB2+/ERBB3 + CTCs AT were a strong predictor for a reduced PFS, with a dominating influence of EGFR and ERBB3 BT but ERBB2 and ERBB3 AT.