MUC1 and gastric cancer: In this case–control study, we investigated the co-expression of PGC, MUC1 and MUC2 in situ in the same group of cases in the SG-AG-GC sequence, as well as in different histological types of GC in order to find molecular phenotypes of gastric cancer and precancerous disease and further explore the potential co-function of PGC, MUC1 and MUC2 in the occurrence and development of gastric cancer.