The explanation for this finding may be that previous ERα studies did not restain both the primary and metastatic lesions [3,5,8,10,11], used ligand-binding assays [2,3,7,10] (where the result is influenced by differences in the percentage of non-tumor cells in the samples), or included bone metastases that may suffer from false negative IHC results due to decalcification [2,4,6,8-10,12]. Here, ESR1 is linked to neoplasm.