ERBB2 and breast cancer: Ensuing from its impact on cell proliferation,25 this supports that TROP2 protein expression may be associated with more aggressive tumor biology,26 despite no correlations being found in other studies with luminal BC subtype21 or TNBC.28 Moreover, we demonstrated adverse relationship between TROP2 protein expression and ER-status in pre- and post-NAC in HR+/HER2− BC.