Next, we correlated the relative expression of the steroid hormone receptors oestrogen receptor-α (ER-α) or -β (ER-β), progesterone receptor (PR), and androgen receptor (AR) with in vitro response to lapatinib, because recent studies suggest that EGFR inhibitors may be particularly active in a subset of breast tumours described as ‘triple negative’ (ie, negative ER, PR, and HER2 expression) (Finn et al, 2006). Here, PGR is linked to breast neoplasm.