For example, trastuzumab is only given to the subgroup of breast cancer patients who are human epidermal growth factor receptor 2 (HER‐2) positive, as it is known to lock on to the HER‐2 protein, block the receptor, and stop the cells from dividing and growing.3 It is therefore considered unnecessary for those who are HER‐2 negative. Here, ERBB2 is linked to breast carcinoma.