Immunohistochemistry & Special Stains Flashcards
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Read the first 7 Immunohistochemistry & Special Stains flashcards as text
Which antigen retrieval method uses a microwave or pressure cooker with citrate buffer to unmask epitopes?
Answer: Heat-induced epitope retrieval (HIER)
HIER uses heat applied in citrate buffer (pH 6) or EDTA buffer (pH 9) to reverse formalin cross-links and unmask epitopes.
In the ABC (avidin-biotin complex) IHC detection method, which molecule bridges the primary antibody signal to the enzyme?
Answer: Biotinylated secondary antibody plus preformed avidin-biotin-enzyme complex
The ABC method uses a biotinylated secondary antibody that binds the preformed avidin-biotin-enzyme complex, amplifying signal.
A Masson's trichrome stain produces which color combination for collagen versus muscle?
Answer: Collagen blue/green, muscle red
Masson's trichrome stains collagen blue or green and muscle (cytoplasm) red, with nuclei staining dark.
Which special stain is used specifically to demonstrate fungi, including Pneumocystis jirovecii, in tissue sections?
Answer: Grocott methenamine silver (GMS)
GMS (Gomori methenamine silver) stains fungal cell walls black by reducing silver ions, and is the preferred stain for Pneumocystis.
Endogenous biotin activity is a common source of background in IHC. Which tissue type is most problematic?
Answer: Kidney and liver
Liver and kidney contain high levels of endogenous biotin, causing non-specific background in biotin-based detection systems.
The Periodic Acid-Schiff (PAS) stain highlights which tissue components?
Answer: Glycogen, mucins, and basement membranes
PAS oxidizes vicinal diols in polysaccharides to aldehydes, which react with Schiff reagent to produce a magenta color in glycogen, mucins, and basement membranes.
Which IHC marker is characteristically positive in Merkel cell carcinoma and has a distinctive paranuclear dot pattern?
Answer: CK20
CK20 shows a paranuclear dot pattern in Merkel cell carcinoma, distinguishing it from small cell lung carcinoma (CK20-negative).
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