ERBB2 and breast cancer: To date, five trastuzumab biosimilars have already been authorized in Italy for the treatment of patients with HER2-positive early or metastatic BC: Kanjinti® (Amgen, Thousand Oaks, CA, USA), Ontruzant® (MSD), Herzuma® (Mundipharma, Hong Kong, China), Ogivri® (Mylan, Canonsburg, PA, USA), and Trazimera® (Pfizer, New York, NY, USA) [24,25,26,27].