Fat stains can be done on sections prepared with which processing?

• A. Water-soluble processing (water-soluble wax)
• B. Paraffin processing
• C. Cryosectioning
• D. Epon embedding

Answer: (A)

Fat stains work by highlighting lipids, so the lipids must remain in the tissue after processing. Standard paraffin processing uses alcohols and other organic solvents that dissolve and remove lipids, making fat deposits disappear in the sections. Water-soluble processing avoids those harsh solvents, preserving lipids within the tissue and allowing lipid-specific dyes (like Sudan dyes or Oil Red O) to bind to the fat droplets. Epon embedding uses resins and strong solvents that also remove lipids, limiting fat staining. While cryosectioning preserves lipids because it skips dehydration and clearing, the processing choice that reliably enables fat staining in routine practice is water-soluble processing, which maintains the lipid content for visualization.