HER2 gene amplification and overexpression occurs in a numberof different cancers including breast, stomach, ovarian, kidney, prostate,salivary glands, colon, urinary, and lung.26 To image HER2-positive cancer, PET has been the modality of choicefor the clinic due to its high spatial resolution and sensitivity.27 Only upon NbHER2 binding to HER2would FSY selectively react with a target residue of HER2 via proximity-enabledSuFEx reactivity and thus cross-link them irreversibly (Figure 1B). Here, ERBB2 is linked to cancer.