Which staining approach would you use to differentiate smooth muscle from collagen in a biopsy?

• A. Masson trichrome and van Gieson
• B. H&E
• C. Verhoeff's stain
• D. PAS

Answer: (A)

Differential staining of connective tissue versus smooth muscle is best achieved with stains that color these components in distinctly different hues. Masson trichrome is designed for this: smooth muscle fibers stain red while collagen fibers stain green or blue, making it easy to see where muscle bundles lie relative to the connective tissue matrix. Adding van Gieson provides complementary contrast, typically staining collagen pink/red and muscle yellow, which reinforces the separation between the two tissues in the same section. Together, these stains give clear, contrasting visualization that specifically highlights smooth muscle against collagen, which is why they’re considered the best approach for this differentiation.

In contrast, H&E offers general morphology but doesn’t reliably distinguish smooth muscle from collagen because both can appear pinkish with eosin, depending on the context. Verhoeff’s stain targets elastic fibers, not the broader distinction between muscle and collagen, and PAS highlights carbohydrates and basement membranes rather than differentiating muscle from connective tissue.