A human epidermal growth factor receptor 2 (HER2)-targeting nanobody (radiopharmaceutical 68Ga-NOTA-Anti-HER2 VHH1) that has proved efficacy to diagnose primary breast carcinoma by Positron Emission Tomography (PET)/Computed Tomography (CT) imaging in a phase I study [65] is being evaluated to detect breast to brain metastasis in phase II clinical trials (ClinicalTrials.gov NCT03331601). The gene discussed is ERBB2; the disease is breast carcinoma.