Which fixative used in grossing could destroy all lipids on the slide?

• A. 100% Ethanol
• B. 70% Ethanol
• C. Neutral buffered formalin
• D. Acetone

Answer: (A)

Lipids are soluble in organic solvents used during tissue processing, so the fixative that would most aggressively remove lipids is the strongest dehydrating solvent. Absolute ethanol has no water, making it a powerful lipid solvent that dehydrates and dissolves lipids completely. When tissue is fixed or processed with 100% ethanol, any lipids present are effectively extracted, leaving none on the slide.

In contrast, a solution containing water (like 70% ethanol) has less solvent power for lipids, so it would not destroy all lipids. Neutral buffered formalin fixes by crosslinking proteins and does not dissolve lipids, so lipids are less affected by it. Acetone is also a lipid solvent, but in the context of this question, absolute ethanol is the most lipid-destructive option, which is why it’s the correct choice. If you need to preserve lipids for staining, methods like freezing or using lipid-preserving fixatives would be used instead.