Recently, two studies suggested that low or negative PR expression can be used to identify ‘luminal B-like’ cancer, which has a poor outcome and is distinguished from ‘luminal A-like’ cancer in ER-positive/human epidermal growth factor receptor-2 (HER2)-negative cancer (Cancello et al. 2013, Prat et al. 2013). Here, ERBB2 is linked to cancer.