The IHC protocol used for ER analysis by the reference pathology department for the Istituto Oncologico Veneto for BC patients was changed in January 2012; however, no significant difference in the prevalence of low ER expression (ER1–9%) BC before 2012 (12.4%, 18/145) and after 2012 (9.2%; 24/261) was observed (p = 0.308). This evidence concerns the gene ESR1 and breast cancer.