ERBB2 and neoplasm: These results, consistent with several previous studies [3,11,63], suggest that HER2 related tumor heterogeneity may arise as a consequence of basal and luminal cell features and provide evidence supporting the hypothesis that the cell of origin for subgroup 7 tumors may have basal-like features, whereas subgroup10 tumors may arise from progenitor cells that have further differentiated and have features more consistent with luminal-like tumors.