MUC5AC and gastric adenocarcinoma: Differentiated gastric adenocarcinomas can be classified as having either gastric, intestinal, mixed or unclassified mucin phenotype based on the expression of MUC5AC (a marker of foveolar cells), MUC6 (a marker of gastric mucous neck cells and pyloric glands), MUC2 (a marker of intestinal goblet cells), and CD10 (a marker of the brush border of the small intestinal absorptive cells) (Fig. 1).