What fixative and minimum time is recommended before processing?

• A. Formalin 10% neutral buffered for at least 45 minutes
• B. Formalin 10% neutral buffered for 15 minutes
• C. Alcohol 65% for 45 minutes
• D. Xylene for 45 minutes

Answer: (A)

Fixation preserves tissue by stabilizing proteins and stopping autolysis so that cellular detail remains intact through dehydration and embedding. The standard fixative for routine histology is 10% neutral buffered formalin because the buffering prevents pH artifacts and formalin cross-links proteins, preserving morphology reliably for staining and interpretation. Before processing, tissue must be fixed long enough to allow adequate penetration; among common options, this combination provides dependable preservation while remaining compatible with paraffin processing. Alcohol is not ideal as the sole fixative for standard processing and can distort staining, while xylene is a clearing agent, not a fixative. Therefore, using formalin 10% neutral buffered for at least 45 minutes is the recommended approach to ensure proper fixation before processing.