Histology Certification Specimen Preparation 2 — Questions and Answers
Question 1: What is the primary purpose of mordanting in histological staining?
- To dehydrate the tissue
- To link the dye to tissue components (Correct answer)
- To remove paraffin wax
- To decalcify bone specimens
Correct answer: To link the dye to tissue components
A mordant forms a bridge between the dye and tissue, improving dye binding and staining intensity.
Question 2: Which fixative is most appropriate for preserving glycogen in tissue specimens?
- 10% neutral buffered formalin (Correct answer)
- Carnoy's fixative
- Zenker's fixative
- Bouin's fixative
Correct answer: 10% neutral buffered formalin
10% neutral buffered formalin preserves glycogen adequately because it avoids the alcoholic fixatives that dissolve this carbohydrate.
Question 3: What problem occurs when tissue is processed through graded alcohols too rapidly?
- Over-fixation artifact
- Inadequate dehydration leaving residual water (Correct answer)
- Excessive shrinkage and hardening
- Lipid dissolution
Correct answer: Inadequate dehydration leaving residual water
Rushing through graded alcohols leaves residual water that prevents complete infiltration of the clearing agent and paraffin.
Question 4: The 'clearing' step in tissue processing refers to:
- Bleaching tissue to remove pigment
- Replacing alcohol with a paraffin-miscible solvent (Correct answer)
- Removing formalin from tissue
- Washing stained sections to remove excess dye
Correct answer: Replacing alcohol with a paraffin-miscible solvent
Clearing replaces the dehydrating agent (alcohol) with a solvent such as xylene that is miscible with both alcohol and paraffin wax.
Question 5: Which embedding medium is preferred for cutting frozen sections in an emergency intraoperative setting?
- Paraffin wax
- OCT compound (Correct answer)
- Celloidin
- Epoxy resin
Correct answer: OCT compound
OCT (Optimal Cutting Temperature) compound is the standard cryostat embedding medium that supports frozen tissue during sectioning.
Question 6: A section shows excessive chatter marks (parallel lines) across the tissue. The most likely cause is:
- Tissue underfixed
- Dull or nicked microtome blade (Correct answer)
- Incorrect xylene clearing
- Excess paraffin in the block
Correct answer: Dull or nicked microtome blade
Chatter marks are caused by vibration during cutting, most commonly from a dull or nicked blade edge.
Question 7: What is the recommended storage temperature for paraffin tissue blocks to preserve antigen integrity for future IHC?
- –80°C
- –20°C
- 4°C (Correct answer)
- Room temperature (20–25°C)
Correct answer: 4°C
Paraffin blocks should be stored at 4°C to slow antigen degradation while avoiding freeze-thaw damage to tissue morphology.
Histology Certification Specimen Preparation 2
What is the primary purpose of mordanting in histological staining?