CEACAM5 and gastric cancer: Carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) have been confirmed as reliable tumor markers that can be used for the early diagnosis and postoperative monitoring of GC, and regular measurements are recommended (Wang et al. 2016b, a; Nam et al. 2013; Shimada et al. 2014).