Two thousands nine hundred thirty three patients (17.6%) had a metastatic biopsy performed at diagnosis or within the next 6 months, among whom 1677 (main study population, 10.0% of the whole cohort) had HR and/or HER2 status available on both MBC biopsy and primary tumour samples (see flow chart, Fig. 1). This evidence concerns the gene ERBB2 and neoplasm.