If acetic acid is used as a fixative alone, what happens to tissue?

• A. Tissue will swell
• B. Tissue will shrink
• C. Tissue will harden
• D. Tissue will become brittle

Answer: (A)

Acetic acid, used alone as a fixative, acts as a coagulative fixative that markedly increases tissue hydration. It penetrates quickly and disrupts cellular proteins, allowing water to enter and cause the tissue to swell. This swelling distorts the tissue architecture but preserves certain cellular details, especially nuclei. Because of this mechanism, tissue will puff up rather than shrink, harden, or become brittle when fixed with acetic acid alone. Shrinking, hardening, or brittleness are more typical of other fixatives or processing steps that remove water or create strong cross-links.