Which stain requires frozen tissue sections for proper visualization?

• A. Cajal
• B. Holmes
• C. PTAH
• D. Bodian

Answer: (A)

The sensation you’re testing here is how certain neural silver stains depend on the tissue preparation to reveal fine neuronal details. The Cajal stain uses silver impregnation to visualize entire neurons, including their cell bodies and long processes. This method is extremely sensitive to how the tissue has been processed, and optimal visualization happens when the tissue is kept in a state close to its natural, hydrated form. Frozen sections preserve tissue water content and minimize the dehydration and chemical alterations that can occur with paraffin processing, allowing the silver impregnation to penetrate and deposit properly in neural elements. That’s why this stain is typically performed on frozen sections.

The other stains—Holmes, PTAH, Bodian—are commonly used on fixed, routinely processed tissue (paraffin or resin-embedded) and do not require freezing for proper visualization.