ERBB2 and breast cancer: Taken into account complex genetic patterns in BC that arise from aneusomy of chromosome 17 (including polysomy and monosomy), co-localization of the CEP17 and the HER2 signals as well as intratumoral genetic heterogeneity and supposedly discordant FISH results [39], [40], [41], [42], our results provide only an indirect speculation and not a proof that high HER2/CEP17 ratios contribute to trastuzumab resistance.