While it exhibited reduced in vitro and in vivo tumor cell retention, the ability of [18F]RL-I-2Rs15d to being a HER2 epitope distinct from that recognized by the HER2-targeted therapeutic antibodies trastuzumab and pertuzumab makes it ideally suited for the PEC/CT-based assessment of the HER2 status of patients who have undergone treatment with either of these mAbs (Zhou et al. 2017). The gene discussed is ERBB2; the disease is neoplasm.