Histology Certification Specimen Preparation 3 — Questions and Answers
Question 1: Which of the following best describes the role of xylene in standard tissue processing?
- Primary fixative agent
- Dehydrating agent
- Clearing agent miscible with paraffin (Correct answer)
- Nuclear counterstain solvent
Correct answer: Clearing agent miscible with paraffin
Xylene is a clearing agent that removes alcohol from tissue and is fully miscible with melted paraffin wax.
Question 2: When processing a core needle biopsy, the cassette used should be:
- A standard large cassette to allow tissue expansion
- A biopsy/mesh cassette to prevent tissue loss (Correct answer)
- An open-top cassette for better reagent penetration
- Any standard cassette if wrapped in paper
Correct answer: A biopsy/mesh cassette to prevent tissue loss
Biopsy mesh cassettes trap small tissue fragments, preventing loss during agitation in automated processors.
Question 3: The pH of 10% neutral buffered formalin (NBF) should be maintained at approximately:
- 4.5–5.0
- 5.5–6.0
- 6.8–7.2 (Correct answer)
- 8.0–8.5
Correct answer: 6.8–7.2
NBF is buffered to near-neutral pH (6.8–7.2) to minimize formalin pigment artifact and preserve antigenicity.
Question 4: Decalcification with strong mineral acids (e.g., HCl) compared to EDTA-based decalcification:
- Preserves DNA for molecular studies better
- Is faster but causes more tissue and nuclear damage (Correct answer)
- Is preferred for IHC staining
- Requires a longer processing schedule
Correct answer: Is faster but causes more tissue and nuclear damage
Strong acid decalcification is rapid but degrades tissue morphology and nucleic acids, making EDTA preferable when downstream molecular or IHC studies are planned.
Question 5: Which artifact results from air drying a smear before fixation in cytological preparations?
- Increased nuclear detail
- Cellular swelling and poor nuclear staining (Correct answer)
- Better preservation of cytoplasmic granules
- Improved Papanicolaou staining results
Correct answer: Cellular swelling and poor nuclear staining
Air drying before fixation causes cells to swell and nuclei to stain poorly, degrading cytological detail.
Question 6: Prolonged over-fixation in formalin primarily leads to:
- Tissue autolysis
- Excessive cross-linking that masks antigens (Correct answer)
- Dissolution of lipids
- Tissue softening and fragmentation
Correct answer: Excessive cross-linking that masks antigens
Over-fixation creates excessive methylene bridge cross-links that mask epitopes, reducing IHC staining sensitivity.
Question 7: What is the purpose of a 'flotation bath' in histological sectioning?
- To rinse residual deparaffinization solvent from slides
- To float and flatten paraffin ribbons for mounting on slides (Correct answer)
- To heat-fix sections to coated slides
- To hydrate tissue before staining
Correct answer: To float and flatten paraffin ribbons for mounting on slides
Warm water in the flotation bath causes paraffin ribbons to expand and flatten, eliminating folds before mounting on glass slides.
Histology Certification Specimen Preparation 3
Which of the following best describes the role of xylene in standard tissue processing?