ER genomic binding in endometrial cancers that arose after tamoxifen treatment of breast cancer look more like ER binding in breast tumors when compared to ER binding in tamoxifen unassociated endometrial tumors, but the effect is subtle with ER binding across all endometrial tumors clustering together and away from the breast tumors regardless of tamoxifen treatment [106]. This evidence concerns the gene ESR1 and breast neoplasm.