H&E vs. PAS Stain: Key Differences in Histopathology Diagnosis
H&E (Hematoxylin & Eosin) stains nuclei blue and cytoplasm pink, giving the classic tissue map pathologists read first. PAS (Periodic Acid–Schiff) turns carbohydrates magenta, highlighting basement membranes, fungi, and glycogen that H&E can miss.
Trainees grab whichever slide is on the scope, so pink-purple H&E and hot-pink PAS can look deceptively similar under bad light. In daily sign-out, a missed fungal wall on H&E alone can delay therapy, so labs reflex to PAS when sugar-rich structures are suspected.
Key Differences
H&E uses two dyes for general morphology; PAS employs Schiff reagent after periodic acid oxidation to tag polysaccharides. H&E is the universal first pass, while PAS is a targeted special stain ordered only when glycogen, mucin, or fungal walls need spotlighting.
Which One Should You Choose?
Start every case with H&E to screen architecture. Add PAS only when you suspect fungal infection, glycogen storage disease, or basement-membrane thickening. Most labs batch PAS slides, so request early; delayed ordering can add days to diagnosis.
Examples and Daily Life
Think H&E like a city map, PAS like a tourist overlay that marks every bakery (sugars). A liver biopsy showing pale H&E cytoplasm hints at glycogen excess—PAS then confirms magenta-packed hepatocytes. In oral thrush, H&E shows inflammation while PAS lights up Candida walls, guiding antifungal choice.
Can PAS replace H&E?
No. PAS is a focused carbohydrate probe; H&E remains the universal structural baseline.
Why does PAS turn magenta?
Periodic acid breaks sugar rings, freeing aldehydes that bind Schiff reagent, creating the magenta color.