ERBB2 and carcinoma: This means that the group of HER2 amplification-negative carcinomas comprise a subgroup of HER2 genetic heterogeneity-positive carcinomas that harbor a significant subpopulation (>5%) of tumor cells with HER2 amplification but do not qualify for trastuzumab treatment based on current recommendations (HER2/CEP17 ratio – calculated on the overall population – below 2.2) (Ohlschlegel et al., 2011).