ERBB2 and cancer: As many data suggest that luminal and non-luminal HER2 positive breast cancers are different entities with regard to their biology and response to therapies [11, 12] and hormonal receptors are important targets also in HER2-positive cancers, efficacy of the combination of endocrine therapies (ET) with HER2 directed agents was an obvious and relevant question to ask in clinical trials addressing this population.