The periodic acid-Schiff stain reveals the mucous neck cells
readily. These cells produce mucus to protect the epithelium of
the stomach from the erosive effects of the very acidic contents.
The cells are mostly located at the necks of the glands (as their name implies) and their product is discharged into the pits to cover and protect them as best it can. The deeper regions of the glands show little or no PAS positive reaction, the mucous cells the most, and there is a considerable amount on the surface, attributable to the secretion.
Fundic stomach; PAS stain, paraffin section, 200x
