Which of the following is NOT listed as a lipid stain for lipoprotein visualization?

• A. Oil Red O
• B. Sudan Black B
• C. Sudan III
• D. Hematoxylin

Answer: (D)

Lipids are visualized with fat-soluble dyes that selectively bind lipid-rich structures. Oil Red O is a red dye used on frozen tissue to stain triglycerides and lipids. Sudan Black B and Sudan III are also fat-soluble dyes that bind lipids, providing contrast for lipoproteins. Hematoxylin, on the other hand, is a basic dye that stains acidic structures like nucleic acids in cell nuclei and is not used to visualize lipids. In routine paraffin sections, lipids are removed during processing, so lipid visualization relies on cryosections with these lipid-specific stains rather than hematoxylin. Therefore, the option that is not a lipid stain is hematoxylin.