Which fixative is commonly used for the stains listed (fixation step across techniques)?

• A. 10% Neutral Buffered Formalin (NBF)
• B. Bouin's fixative
• C. Alcohol
• D. Zenker's solution

Answer: (A)

10% Neutral Buffered Formalin is the most versatile fixative for fixation steps used across different staining techniques. It preserves tissue architecture by forming cross-links between proteins, which stabilizes cellular structures without overly distorting morphology. Keeping the pH neutral prevents artifacts that acidic fixatives can cause, helping maintain consistent staining results. This combination makes it compatible with a wide range of stains and downstream processes, including routine H&E, special stains, and many immunohistochemical methods that rely on preserved antigenicity after fixation.

Other fixes have drawbacks in broad use: Bouin’s fixative includes picric acid and acetic acid, which can yellow tissue and complicate washing and downstream staining. Alcohol fixatives coagulate proteins and can cause tissue hardening and shrinkage, compromising morphology for some stains. Zenker’s solution is mercury-based and toxic, with compatibility issues for modern staining workflows.