Which fixative is known to preserve erythrocytes in bone marrow sections?

• A. Helly
• B. Bouin
• C. Zenker
• D. Carnoy

Answer: (A)

Preserving delicate cellular elements in bone marrow relies on a fixative that rapidly immobilizes proteins and membranes without dissolving the cells. Helly fixative, which includes mercuric chloride with formaldehyde and acetic acid, cross-links and stabilizes cellular components, keeping erythrocytes intact and well delineated in bone marrow sections. This allows accurate visualization of erythroid precursors and the overall marrow architecture. Other fixatives, such as Bouin’s (picric acid–containing) or Zenker’s (potassium dichromate with mercuric chloride), can alter or dissolve erythrocytes or create artifacts that obscure RBC morphology. Carnoy’s fixative (ethanol–chloroform–acetic acid) tends to dehydrate and shrink cells and can distort RBCs, making Helly the best choice for preserving erythrocytes in marrow histology.