CEACAM5 and neoplasm: Currently, various new tumor markers are being developed, but the more recognized gastric cancer tumor markers are carcinoembryonic antigen (CEA) (Ishigami et al., 2001; Zhang et al., 2021), carbohydrate antigen (CA) (Gaspar et al., 2001), CD44V9 (Mashima et al., 2019), miRNAs (Khandelwal et al., 2019), and programmed death ligand 1 (PD-L1) (Wang et al., 2019).