Acid fuchsin is used in which staining procedures?

• A. Masson trichrome, van Gieson
• B. Gomori trichrome
• C. Verhoeff
• D. Aldehyde fuchsin

Answer: (A)

Acid fuchsin acts as the red counterstain in certain connective tissue stains, highlighting muscle and cytoplasm so collagen stands out with a contrasting color. In the Masson trichrome method, acid fuchsin provides the red hue for muscle and cytoplasm, while a second dye colors collagen blue. In the van Gieson technique, acid fuchsin again stains muscle and cytoplasm red, with picric acid giving collagen its yellow background. Because both of these stains rely on acid fuchsin to produce that red coloration for muscle/cytoplasm, they are the correct choices. Other options involve different dyes or focus on elastin or other tissue components, not the same red counterstain role.