The PAS control slide for neutral mucins corresponds to which tissue?

• A. Small Intestine
• B. Stomach
• C. Colon
• D. Esophagus

Answer: (A)

PAS highlights neutral mucins because they are rich in neutral glycoproteins that stain magenta. A control tissue for neutral mucins should come from a source known to secrete neutral mucins consistently. The proximal small intestine, especially the duodenum, has Brunner’s glands that produce alkaline mucus highly rich in neutral mucins, making it a reliable reference for this staining pattern. That’s why this tissue serves as the best control for neutral mucins in PAS. In contrast, mucins of the colon are predominantly acidic, and esophageal mucins are not the standard neutral mucin control, whereas the stomach does contain neutral mucins but is less specific as a control source in many practice sets. So the small intestine best fits the neutral mucin control slide.