Hard and brittle biopsy specimens after zinc formalin fixation will result if the specimens are dehydrated with what?

• A. Dehydrated with >70% alcohol
• B. Dehydrated with 60% alcohol
• C. Dehydrated with 95% alcohol only
• D. Dehydrated with absolute alcohol

Answer: (A)

High-concentration alcohol during dehydration can cause excessive shrinkage and hardening of tissue that has been fixed with zinc formalin. Zinc formalin increases tissue rigidity through cross-linking, so removing water too quickly with alcohols above about 70% pulls the tissue tighter and makes it become hard and brittle. To avoid this, dehydration should be done gradually in a graded series, starting with lower ethanol concentrations and increasing step by step, rather than jumping to high-strength alcohols. Absolute or very high alcohol levels are the most aggressive and will worsen brittleness, which is why using alcohol concentrations above 70% tends to produce hard, brittle specimens in zinc-formalin-fixed tissue.