Which stain highlights collagen fibers?

• A. Hematoxylin and eosin
• B. Ziehl-Neelsen acid-fast stain
• C. PAS
• D. Masson's trichrome

Answer: (D)

Masson's trichrome stands out because it uses multiple dyes to color different tissue components separately, making collagen fibers appear blue (or green, depending on the protocol). This contrast lets you see the collagen network clearly against muscle or cytoplasm, which stain red, and nuclei, which stain dark. That specificity is why it’s the go-to stain for evaluating connective tissue content, fibrosis, and scar formation.

Hematoxylin and eosin gives a general view of tissue architecture, with nuclei blue and most other structures pink, but collagen isn’t highlighted distinctly. PAS highlights carbohydrates and basement membranes, not collagen specifically. Ziehl-Neelsen targets acid-fast organisms, not connective tissue.