A Feulgen stain is required on a section of Bouin fixed lymph node. What is the best course of action?

• A. Proceed With The Stain As Planned
• B. Ask If There Is Tissue In Another Fixative
• C. Re-Fix The Tissue In Formalin
• D. Discard The Tissue

Answer: (B)

Feulgen staining is DNA-specific and depends on a clean acid hydrolysis step to reveal aldehyde groups on DNA, which then react with Schiff’s reagent to produce a magenta nucleus. Fixatives like Bouin, which is picric acid–based, can leave residues and alter nuclear chemistry in ways that interfere with the hydrolysis and Schiff reaction, leading to weak, uneven, or non-specific staining. Because this can compromise the reliability of the result, the best approach is to check whether tissue from the same sample is available in a fixative known to be compatible with the Feulgen reaction (such as formalin- or alcohol-fixed tissue) and perform the stain on that material. If such tissue exists, use it for the Feulgen stain; if not, request tissue fixed in a suitable fixative rather than attempting the stain on Bouin-fixed tissue.