When performing a Feulgen stain on Bouin-fixed lymph node, what is the recommended action?

• A. Proceed With The Staining As Planned
• B. Ask If There Is Tissue In Another Fixative
• C. Switch To Hematoxylin Staining First
• D. Use A Different Stain Entirely

Answer: (B)

Feulgen staining is highly fixation-sensitive because it relies on acid hydrolysis to generate aldehyde groups on DNA, which Schiff’s reagent then detects. Bouin fixative contains picric acid and can leave residues that interfere with the Feulgen reaction, making results unreliable. Because of that, the appropriate step is to check whether there is tissue available fixed in a fixative compatible with Feulgen and use that tissue for staining. If no compatible tissue is available, you’d need to obtain a specimen fixed in a suitable fixative or consider a different staining approach.