If tissue is not well cleared and infiltrated, what adjustment might improve processing?

• A. Add aliphatic hydrocarbon and delete one of the 95% alcohols
• B. Increase fixation time
• C. Use more formalin
• D. Skip xylene steps

Answer: (A)

When tissue isn’t clearing well, the key issue is that the dehydration solvent and the clearing agent aren’t exchanging efficiently, so paraffin can’t penetrate properly. Introducing an aliphatic hydrocarbon as the clearing solvent provides a solvent that is more effective at displacing the residual dehydrating alcohol and is miscible with paraffin, helping the tissue become transparent and ready for infiltration. Deleting one of the 95% alcohol steps reduces the amount of dehydrating solvent present, which eases the transition to clearing and improves solvent exchange, enhancing infiltration.

Options that increase fixation time or add more formalin would tend to stiffen tissue and slow or hinder penetration, not improve clearing. Skipping the clearing step would remove the necessary agent for making the tissue receptive to paraffin, so infiltration would fail.