MLT GlobeHistopathology: Special stains – page 2
53 Histopathology MCQs on Special stains with answers and explanations.
Glycogen, neutral mucins and glycoproteins are all magenta with which method?
Periodic acid oxidizes 1,2-glycols to aldehydes that Schiff reagent colours magenta. Sudan black B stains lipids.
In the PAS reaction, what does the periodic acid step do?
Periodic acid oxidizes 1,2-glycol groups to aldehydes, which Schiff reagent then colours magenta. Diastase is used to digest glycogen.
In a correctly stained Verhoeff–van Gieson section of an artery, collagen should appear:
VVG gives black elastic fibres and nuclei, red collagen (acid fuchsin) and yellow muscle (picric acid); yellow-orange collagen signals a staining fault.
Paired sections are stained with PAS with and without diastase. Material lost from the diastase-treated section indicates:
Diastase digests glycogen, so PAS positivity that disappears after digestion is glycogen; mucins and fungi stay PAS-positive.
A biopsy of a poorly differentiated carcinoma shows pink-red intracytoplasmic droplets with Mayer's mucicarmine. This indicates:
Mucicarmine selectively stains epithelial mucins (and the capsule of Cryptococcus). It is used to identify mucin-producing adenocarcinomas; connective tissue mucins stain weakly or not at all.
In a sexual assault examination, which stain is commonly used on smears to highlight spermatozoa, giving red heads and green tails?
The Christmas tree stain colours sperm heads red and midpieces/tails green against a background of epithelial cells. It is a standard forensic screening method alongside acid phosphatase and PSA tests.
With methyl green–pyronin staining, what colours do nuclear DNA and cytoplasmic RNA take?
Methyl green binds polymerized DNA (green-blue) and pyronin Y binds RNA (red). Plasma cells, rich in RNA, show red cytoplasm; ribonuclease pretreatment abolishes the red.
A good positive control tissue for demonstrating free and esterified cholesterol is:
The adrenal cortex is rich in cholesterol and its esters used for steroid synthesis, making it a standard control for cholesterol methods such as the Schultz (Liebermann-Burchard) technique.
Nissl substance in neurons is usually demonstrated with which stain?
Cresyl fast violet binds the RNA of Nissl bodies (rough ER), colouring them purple. Oil red O shows fat, Alcian blue acid mucins and Perls' ferric iron.
In the Martius scarlet blue (MSB) method, collagen stains:
MSB shows fibrin red, red cells yellow and collagen blue. It is used to assess the age of fibrin in thrombi.
Which enzyme is the classic histochemical marker for lysosomes?
Lysosomes contain acid hydrolases, typically shown by acid phosphatase (and arylsulfatase). Alkaline phosphatase marks brush borders and osteoblasts; the others are mitochondrial.
Mast cell granules stain red-purple with toluidine blue, a blue dye. This phenomenon is called:
Metachromasia is staining of tissue in a colour different from the dye itself, caused by dye stacking on highly anionic substances such as heparin. Orthochromatic staining matches the dye colour.
Unfixed cryostat sections for Oil red O are fixed briefly in which solution to preserve lipids?
Formalin with calcium ions stabilizes lipids, especially phospholipids. Alcohol, acetone and Carnoy's are lipid solvents and would extract the fat.
A Giemsa-stained bone marrow trephine shows poor nuclear staining and little cytoplasmic differentiation. The most likely cause is:
Romanowsky stains depend critically on pH (about 6.8); an incorrect buffer weakens nuclear and cytoplasmic contrast. Giemsa does not require ripening.
In Hale's method, acid mucins bind a reagent whose ferric ions are then revealed by the Prussian blue reaction. That reagent is:
Colloidal ferric ions bind carboxylated and sulfated mucins and are shown blue with acid ferrocyanide. Diastase digests glycogen and dimedone blocks aldehydes.
To see nuclear detail in a heavily pigmented melanoma, melanin is bleached with which oxidizer?
Melanin is bleached by oxidizers such as potassium permanganate (or hydrogen peroxide). Oxalic acid then removes the brown manganese deposit left behind.
A liver biopsy is examined for Wilson disease. The most sensitive histochemical method for copper uses:
Rhodanine gives red-orange granules with copper and is the most sensitive. Orcein stains copper-associated protein, and chloranilic acid is for calcium oxalate.
In Luxol fast blue staining for myelin, differentiation uses:
Lithium carbonate followed by 70% alcohol removes dye from grey matter while myelin keeps its blue. Repetition continues until the contrast is sharp.
The blue precipitate formed in the Perls' Prussian blue reaction is:
Ferric ions react with ferrocyanide to form insoluble ferric ferrocyanide (Prussian blue). Ferrous ferricyanide is Turnbull blue, the product for ferrous iron.
Formalin-fixed sections are often treated with Bouin's solution before Masson trichrome. What is Bouin's role here?
Bouin's post-fixation mordants tissue so the acid dyes give brighter, sharper trichrome colours.