The acid secreting (oxyntic) parietal cells of the gastric body/fundic mucosa have abundant eosinophilic ('pink') cytoplasm while the protein producing chief cells have basophilic ('blue') cytoplasm . Why?
The production of HCl requires enormous amounts of energy so acid-producing parietal cells are jam packed with energy producing mitochondria; these stain strongly with acidic dyes including eosin (the 'E' in H&E). The main function of chief cells is the production of the (pre-)protein pepsinogen so chief cells are packed with ribosome lined (rough) endoplasmic reticulum; ribosomes stain with basic dyes including haematoxylin (the 'H' in H&E)
The incidental 2mm polyp shows histological features of benign fundic gland polyp.
The gastric mucosa is focally thickened with a polypoid outline, with underlying rounded to angular dilated glands.
The polyp is formed by loose aggregates of dilated glands within oxyntic (acid-secreting) mucosa ie. gastric fundus and body.
The dilated glands are lined predominantly by parietal cells and smaller proportions of chief cells.