In particular, 89Zr-labeled trastuzumab (Herceptin®), one the most widely used mAb in clinical oncology, has been used to evaluate the HER2 status for patient selection and to assess the response of BC patients to anti-HER2 therapy [33,34] and represents an encouraging step towards the routine use of PET to accurately assess the expression of HER2 over time. Here, ERBB2 is linked to breast cancer.