Two [68Ga]Ga-NOTA-sdAb tracers are currently in clinical investigation as PET tracer: the [68Ga]Ga-NOTA-anti-HER2 tracer [8], for HER2 positive metastatic breast cancer diagnosis, including brain metastases, (EudraCT 2016-002164-13—NCT03924466; EudraCT 2015-002328-24—NCT03331601) and the [68Ga]Ga-NOTA-anti-MMR tracer [9], targeting the Macrophage Mannose Receptor (MMR), for detection and imaging of Tumor Associated Macrophages (TAM’s) (EudraCT 2017-001471-23—NCT04168528). The gene discussed is MRC1; the disease is breast carcinoma.