ERBB2 and breast cancer: Triple‐negative breast cancer (TNBC) is an aggressive subtype of breast cancer accounting for 15–25% of all breast cancers, and 24% of newly diagnosed cases.[1, 2] Clinical TNBCs lack the expression of oestrogen (ER), progesterone (PR), and HER2 receptors, which means patients are not suitable for either hormone or anti‐HER‐2 therapy.