Which fixative may lyse erythrocytes?

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

Answer: (A)

Red blood cells are highly susceptible to fixation-induced lysis when strong acids are present in the fixative. Bouin’s solution contains acetic acid along with picric acid and formaldehyde. The acetic acid component disrupts the RBC membrane and alters osmotic conditions, causing erythrocyte lysis and leaving behind ghost or absent red cells in tissue sections. The picric and formaldehyde components fix the rest of the tissue, but they don’t prevent this lysis effect driven by the acetic acid.

The other fixatives listed rely on different chemistry or metal-containing components that do not produce the same erythrocyte lysis pattern under typical use, so they are less likely to lyse red cells.