MLT GlobeHistopathology: Special stains – page 3
53 Histopathology MCQs on Special stains with answers and explanations.
Masson trichrome typically uses which dye combination?
Weigert's iron haematoxylin stains nuclei, Biebrich scarlet–acid fuchsin stains muscle red and aniline blue stains collagen blue.
A colonic biopsy is suspected of amoebic colitis. Which stain best highlights Entamoeba histolytica trophozoites?
Trophozoites are rich in glycogen and glycoproteins, so they stand out magenta with PAS. Perls, Congo red and Masson–Fontana detect iron, amyloid and melanin.
Sections keep detaching from slides during a harsh staining procedure. What protective coating can be applied?
Dipping slides in dilute celloidin forms a film that holds sections in place; glycerin and oils prevent adhesion.
Heidenhain's iron haematoxylin is classically used to demonstrate:
Heidenhain's iron haematoxylin gives crisp black staining of striations and mitochondria after careful differentiation.
Why are alum haematoxylins such as Harris or Mayer's unsuitable before a van Gieson stain?
Acidic picro-fuchsin decolourises alum haematoxylin, so an acid-resistant iron haematoxylin (Weigert's) is used instead.
Which glycogen stain is considered empirical, meaning its mechanism is not fully explained by known chemical reactions?
Best's carmine works well for glycogen but its binding mechanism is not clearly understood. PAS, Perls' and Feulgen are histochemical reactions with defined chemistry.
A frozen section is stained with a Sudan dye at room temperature, but crystalline cholesterol deposits do not colour. Why?
Sudan dyes work by dissolving in lipid; solid or crystalline lipids at staining temperature take up little dye and remain unstained or weakly stained.
Which method specifically demonstrates phospholipids, staining them blue-black?
Baker's acid hematein method is the classic phospholipid technique, with pyridine extraction as a control. Oil red O shows neutral fats red; PAS stains carbohydrates.
Which reagent is NOT part of Best's carmine stock solution?
Best's carmine stock contains carmine, potassium carbonate and potassium chloride boiled in water, with ammonia added. Formaldehyde is not an ingredient.
In Verhoeff's elastic stain, how is the overstained section differentiated?
Dilute ferric chloride pulls dye from the lake in less avid structures, leaving elastic fibres black. Progress is checked microscopically.
In Weil's myelin stain, borax–ferricyanide differentiates the haematoxylin by:
Potassium ferricyanide is an oxidizer that removes the lake from non-myelin structures; borax buffers the solution.
Alkaline Congo red solutions for amyloid include which salt to suppress background staining?
Sodium chloride in alkaline alcoholic Congo red (Puchtler) reduces non-specific binding, making amyloid staining more selective.
The azo-dye method for acid phosphatase depends on enzymatic hydrolysis of which substrate?
The enzyme releases alpha-naphthol, which couples with a diazonium salt to form a coloured azo dye at the site of activity.