Interestingly, in the remaining two patients with suggestive foci on [89Zr]Zr-trastuzumab PET/CT, biopsies confirmed the presence of HER2-positive metastasis, indicating the potential of radiolabelled HER2 antibody to detect unsuspected HER2 distant metastasis in HER2-negative primary BC [95]. The gene discussed is ERBB2; the disease is breast cancer.