Based on the fact that GP88 expression in ER+ cells was associated with estrogen independence and tamoxifen resistance [17], analysis of GP88 tissue expression in ~600 cases of ER+ IDC in relation with clinical outcomes demonstrated that high GP88 expression (IHC score of 3+) was associated with a 5.9-fold higher hazard of disease recurrence (p < 0.0001) and a 2.5-fold higher mortality hazard (p = 0.0002) compared to patients with no or low tumor GP88 expression [22]. This evidence concerns the gene ESR1 and neoplasm.