Another issue is high disease heterogeneity: unlike primary breast cancer, which has clear markers delineating luminal, A, luminal B, HER-2 enriched and triple negative tumours, defining the best treatment options, prostate cancer has at best been separated into 7 subclasses defined by genomic alterations, which are neither prognostic nor predictive3, although the PAM50 classifier approach has now been used to define, with analogy to breast cancer, subtypes also termed luminal A, B and basal that may be better predictive of therapy response4. Here, ERBB2 is linked to breast cancer.