HT Histology Techniques & Technology 3 — Questions and Answers
Question 1: What is the role of a mordant in histological staining?
- To decolorize background tissue
- To link the dye to the tissue component (Correct answer)
- To fix the tissue before staining
- To differentiate nuclear from cytoplasmic staining
Correct answer: To link the dye to the tissue component
A mordant forms a bridge between the dye and the tissue, creating a stable dye–mordant–tissue complex and intensifying the stain.
Question 2: In the Masson trichrome stain, collagen fibers are demonstrated in which color?
- Red
- Blue or green (Correct answer)
- Yellow
- Black
Correct answer: Blue or green
Masson trichrome stains collagen blue (with aniline blue) or green (with light green), while muscle stains red and nuclei stain black.
Question 3: Which stain is the gold standard for demonstrating amyloid deposits in tissue sections?
- Periodic acid–Schiff (PAS)
- Congo red (Correct answer)
- Alcian blue
- Methenamine silver
Correct answer: Congo red
Congo red stains amyloid salmon-pink and shows apple-green birefringence under polarized light, which is pathognomonic for amyloid.
Question 4: The Prussian blue (Perls') reaction is used to detect which substance in tissue?
- Calcium
- Ferric iron (hemosiderin) (Correct answer)
- Lipofuscin
- Glycogen
Correct answer: Ferric iron (hemosiderin)
Perls' Prussian blue reaction converts ferric iron to ferric ferrocyanide, producing a bright blue precipitate that identifies hemosiderin deposits.
Question 5: Diastase pre-treatment before PAS staining is used to confirm the identity of which tissue component?
- Mucin
- Glycogen (Correct answer)
- Neutral lipids
- DNA
Correct answer: Glycogen
Diastase (amylase) digests glycogen; PAS-positive material that disappears after diastase pre-treatment is confirmed as glycogen.
Question 6: Which fixative is preferred when performing frozen sections for lipid demonstration?
- 10% neutral buffered formalin for 24 hours
- Unfixed fresh-frozen tissue or formalin-fixed frozen sections (Correct answer)
- Zenker's fixative
- Bouin's fixative
Correct answer: Unfixed fresh-frozen tissue or formalin-fixed frozen sections
Lipids are dissolved by organic solvents used in routine paraffin processing, so frozen sections from unfixed or formalin-fixed (not paraffin-processed) tissue are required.
Question 7: In immunohistochemistry, heat-induced epitope retrieval (HIER) is performed primarily to reverse which processing effect?
- Lipid dissolution by organic solvents
- Cross-linking of proteins caused by formalin fixation (Correct answer)
- Dehydration artifact in the tissue
- Antigen degradation caused by microtome sectioning
Correct answer: Cross-linking of proteins caused by formalin fixation
Formalin creates methylene bridges between proteins that mask epitopes; HIER uses heat and buffer to break these cross-links and unmask the epitopes.
HT Histology Techniques & Technology 3
What is the role of a mordant in histological staining?