ERBB2 and neoplasm: This dichotomous classification into HER2-positive and HER2-negative BCs, very useful in the context of anti-HER2 therapies, has currently been shaken up since new anti-HER2 therapies (antibody-drug conjugates, ADC) were shown to be effective in patients with HER2 2+ unamplified and HER2 1+ tumours, which were to date considered as HER2-negative [16–18].