Name a stain that uses a separate formaldehyde reduction step.

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

Answer: (A)

The staining approach for reticular fibers that uses a separate formaldehyde reduction step relies on a two-phase development: first the fibers are silver-impregnated, then a distinct developer containing formaldehyde reduces the silver specifically on the reticular network. This formaldehyde-reduction step provides high-contrast black reticular fibers against a light background, which is characteristic of the Gomori reticulin method. Other stains on the list stain different structures (elastic fibers or basement membranes) and do not employ this separate formaldehyde-reduction development.