Additionally, 18F-labelled anti-HER2 VHHs are not retained in the liver, a frequent site of metastases for HER2-positive breast cancers, which offers a potential advantage compared to other HER2-specific immunoPET agents such as 89Zr-DFO-Trastuzumab, which exhibits significant accumulation in the liver (57). This evidence concerns the gene ERBB2 and breast cancer.