ERBB2 and breast cancer: Considering the in vitro and in vivo data, we expanded our observations using IHC to 180 breast cancer patients, subdivided in four categories with 45 cases each: (i) ER−/PR−/HER2− (triple-negative), (ii) ER+/PR+/HER2+ (triple-positive), (iii) ER+/PR+/HER2− (HR+), and (iv) ER−/PR−/HER2+ (HER2+) (Fig 7A; S1 Table).