Cases with HER2/CEP17 < 2.0 and HER2cn ≥ 4.0 but < 6.0 and cases with HER2/CEP17 ≥ 2.0 and HER2cn < 6.0 serve as independent FISH subgroups in breast cancer with distinct clinicopathological features (Yang et al. 2020). This evidence concerns the gene ERBB2 and breast cancer.