The technique shown is what type of staining?

• A. Immunohistochemical
• B. Physical
• C. Fluorescent
• D. Enzymatic

Answer: (B)

Physical staining is non-specific dye staining that relies on the inherent color and basic binding properties of the dye to tissue components, without employing antibodies, enzyme reactions, or fluorescence. The technique shown produces color through direct dye-tissue interaction and does not involve antigen–antibody binding, enzymatic substrate conversion, or fluorescent labels. That general, non-targeted color distribution is the hallmark of a physical stain.

Immunohistochemical staining would show selective localization where a specific antigen is present (often with a chromogen like DAB producing brown deposits). Fluorescent staining would emit light under excitation, showing bright signals. Enzymatic staining depends on a substrate reacting with an enzyme to yield color. Thus, the image’s non-specific, non-fluorescent appearance without targeted localization aligns with physical staining.