The aim of this pilot study was to assess HER2 gene status by fluorescence in situ hybridisation (FISH) in micrometastatic cells in bone marrow of breast cancer patients and to compare it to HER2 primary tumour status, in order to evaluate if anti-HER2 therapy in adjuvant setting, could be given to patients after an assessment of HER2 status of the primary tumour only. This evidence concerns the gene ERBB2 and neoplasm.