Which stain is used to differentiate granulocyte precursors from leukocytes?

• A. Sudan Black B
• B. Oil Red O
• C. Periodic Acid-Methanamine for Basement Membranes
• D. Verhoeff's Elastic Stain

Answer: (A)

The main idea is that granulocyte lineage cells contain cytoplasmic granules rich in lipids, while many leukocytes (like lymphocytes) do not. Sudan Black B is a lipid-soluble dye that binds to those neutral lipids and phospholipids in the granules of granulocytes and their precursors. Because of this, granulocytic precursors (myeloblasts, promyelocytes, myelocytes, etc.) take up the stain and appear dark, whereas lymphocytes—lacking prominent granules—stain little or not at all. This contrast helps distinguish granulocytic precursors from other leukocytes on bone marrow or peripheral blood smears.

Oil Red O also stains lipids but is used mainly for detecting lipids in frozen tissue sections, not for differentiating hematopoietic cell lineages. Periodic Acid-Methenamine for Basement Membranes targets basement membranes, and Verhoeff’s Elastic Stain highlights elastic fibers. None of these are used to differentiate granulocyte precursors from leukocytes in hematology.