Which stain is used to differentiate between neutral and acidic mucins?

• A. Alcian blue PAS hematoxylin
• B. Hematoxylin only
• C. PAS only
• D. Mucicarmine

Answer: (A)

Differentiating neutral from acidic mucins relies on using stains that react with different chemical components of mucins. Alcian blue binds specifically to acidic mucins (the sulfated and carboxylated glycosaminoglycans) and colors them blue. The PAS reaction, on the other hand, detects carbohydrates in neutral mucins and turns them magenta. When you apply both stains on the same tissue slide, often with a hematoxylin counterstain for nuclei, you can see a clear contrast: acidic mucins appear blue while neutral mucins appear magenta. This combination provides a direct way to distinguish the two mucin types in one section, which is why it’s the best choice for differentiating neutral versus acidic mucins. Other options don’t offer this differential capability on their own—hematoxylin only stains nuclei, PAS alone stains carbohydrates (including some neutral mucins) but not specifically acidic mucins, and mucicarmine stains mucins without reliably separating acid from neutral variants.