The procedure for the reagent paraldehyde uses which stain?

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

Answer: (A)

Paraldehyde is an aldehyde fixative, so tissues fixed with it present aldehyde groups that can be specifically detected by an aldehyde-reactive stain. Aldehyde fuchsin is designed to bind to those aldehyde groups, producing a distinctive color where aldehyde residues are present. That makes it the appropriate stain for the paraldehyde procedure. The other stains are used for different targets—elastic fibers with Verhoeff, reticular fibers with Gomori reticulin, and basement membranes or fungi with periodic acid–methenamine silver—so they aren’t the correct choice for tissues fixed with paraldehyde.