<b>Methods</b>: We performed a retrospective analysis including HER2- mBC patients treated at a single academic center starting from 10 April 2019 (date of European Medicines Agency (EMA) approval of Olaparib for germline breast cancer gene mutant (gBRCAm) HER2- mBC) to 7 September 2021. This evidence concerns the gene ERBB2 and breast cancer.