Which stain is a classic elastic stain that uses ferric chloride as a mordant?

• A. Verhoeff
• B. Aldehyde fuchsin
• C. Gomori reticulin
• D. Periodic acid-methenamine silver

Answer: (A)

The key idea is identifying an elastic fiber stain that uses ferric chloride as the mordant. Verhoeff’s stain achieves this by using iron hematoxylin, where ferric chloride acts as the mordant to bind the stain to elastic fibers. As a result, elastic fibers appear black or very dark, often with nuclei blue-black and other tissues counterstained for contrast (commonly with van Gieson). This ferric chloride–based approach is what makes it the classic elastic stain associated with that mordant.

Other elastic stains exist, such as aldehyde fuchsin, which also highlights elastic fibers but uses a different staining chemistry and mordants, not the ferric chloride–based method. Gomori reticulin relies on silver impregnation to visualize reticular fibers, and periodic acid–methenamine–silver uses silver for basement membranes, so neither depends on ferric chloride as a mordant.