How long should specimens be fixed in 10% neutral buffered formalin for all stations?

• A. 15 minutes
• B. 45 minutes
• C. 60 minutes
• D. 120 minutes

Answer: (A)

Fixation time in formalin determines how well tissue morphology is preserved and how it will behave during processing and staining. Formalin works by cross-linking proteins to stabilize cellular structure, but it must penetrate the tissue to do so. For these stations, using a uniform, shorter fixation time keeps all specimens consistently preserved without pushing into over-fixation, which can dull detail and hinder staining.

A 15-minute immersion in 10% neutral buffered formalin provides enough stabilization for typical small specimens encountered across stations while minimizing the risk that longer times (like 45, 60, or 120 minutes) would over-fix the tissue. Over-fixation can cause excessive hardening, shrinkage, and antigen masking, making sections harder to cut and stains less reliable. So, 15 minutes is chosen to balance adequate fixation with preservation of staining quality and morphology across all stations.