ERBB2 and neoplasm: The numbers of cores in HER2 or Basal tumours were not higher or lower compared with other subtypes (p > 0.1, Kruskal-Wallis test), supporting that the low correlation between core-based and tumour-based scores we observed in HER2 tumours was not due to tumour size but likely reflected a higher level of intra-tumour heterogeneity (Fig. 2B).