CLDN18 and gastric cancer: Among four subtypes of GC [microsatellite instability (MSI), EBV, genomically stable (GS), and chromosomal instability (CIN)] and HER2, CLDN18 expression was significantly and distinctly higher in EBV-associated GC [EBV ( +)], while ERBB2 (HER2) status did not influence CLDN18.2 expression (Fig. 2B).