How are fats typically stained in histology?

• A. Stains for fats are done on frozen sections fixed in neutral buffered formalin
• B. Fats are stained in paraffin sections after dehydration
• C. Fats are stained with osmium tetroxide in all sections
• D. Fats cannot be stained in histology

Answer: (A)

Lipids must be preserved to visualize fats histochemically, and paraffin processing removes fats because it uses dehydration and organic solvents. Because of that, fats are demonstrated on frozen (cryostat) sections where the lipid droplets stay intact long enough to stain with lipid-specific dyes such as Sudan stains or Oil Red O. Brief fixation of the frozen tissue in neutral buffered formalin helps preserve structure without dissolving the lipids, making the staining meaningful.

The other options don’t fit this approach: paraffin sections after dehydration would lose fats during processing, so lipid staining wouldn’t be reliable; osmium tetroxide can fix and stain lipids but is not used universally in all sections and isn’t the standard for routine histology; and fats can indeed be stained when preserved properly, so saying they cannot be stained is incorrect.