The first section of the review will discuss the use of immunoPET in GC targeting the antigens carcinoma-associated antigen (MG7) [14], programmed death-1 (PD-1) [16], cadherin-17 (CDH17) [15], human epidermal growth factor receptors 2 and 3 (HER2 [5,9,21,22,23,24] and HER3 [12]), hepatocyte growth factor (HGF [11]), and the mesenchymal-epithelial transition factor (MET) [10]. The gene discussed is CDH17; the disease is gastric cancer.