Oil Red O staining requires which type of tissue section to visualize lipids?

• A. Paraffin Sections
• B. Frozen Sections
• C. Resin-Embedded Sections
• D. Plastic Sections

Answer: (B)

The key idea is that Oil Red O can stain lipids only if the lipids remain in the tissue. Lipids are dissolved and removed during routine paraffin processing, which uses dehydration and clearing solvents, so paraffin-embedded sections won’t show lipids with Oil Red O. Frozen sections preserve lipids because they skip those solvent steps, keeping neutral lipids intact for the dye to bind and stain red. Resin-embedded or plastic sections involve embedding processes that also remove or obscure lipids, making them unsuitable for this stain. Therefore, frozen sections are the proper choice to visualize lipids with Oil Red O.