The MCF7 (ER+/HER2-), T47D (ER+/HER2-), BT474 (ER+/HER2+) and SKBR3 (ER-/HER2+) cell lines are widely used in breast cancer research as paradigms of the luminal and HER2 immunophenotypes [9,10]. The gene discussed is ERBB2; the disease is breast cancer.