Corroborating the above findings in the clinical setting, immunohistochemical analysis of ER + BC tissue specimens derived from 58 patients revealed that heparanase positivity significantly correlated with higher levels of ERα expression (quantified as in [54] in the tumor tissue): a nearly 2-fold higher proportion of high ERα expression was detected in heparanase-positive versus heparanase-negative tumors (73% vs. 40%, chi-square test p = 0.0135, Figure 7). This evidence concerns the gene ESR1 and breast cancer.