Expansion
H and E for routine work, with special stains for specific components
Mnemonic
Match the stain to what it demonstrates:
- Haematoxylin and eosin - the default. Haematoxylin stains nuclei blue (basophilic), eosin stains cytoplasm pink (eosinophilic)
- Periodic acid-Schiff (PAS) - glycogen, glycoproteins, basement membranes, fungi. Magenta
- Congo red - amyloid, giving apple green birefringence under polarised light
- Ziehl-Neelsen - acid fast bacilli, so mycobacteria. Red on blue
- Prussian blue (Perls) - iron, for haemochromatosis
- Masson’s trichrome - collagen and fibrosis, blue or green
- Gram - bacteria, purple positive and pink negative
- Silver stains - reticulin, fungi (Grocott), neurofibrillary tangles
- Oil red O and Sudan - lipid, requiring frozen sections
“H&E for everything, PAS for sugar, Congo red for amyloid, ZN for TB, Perls for iron.”
Apple green birefringence with Congo red is diagnostic of amyloid and is the single most frequently examined stain result.
Expansion
| Stain | Demonstrates | Appearance |
|---|---|---|
| Haematoxylin and eosin | Routine | Nuclei blue, cytoplasm and collagen pink |
| PAS | Glycogen, glycoprotein, basement membrane, fungi | Magenta |
| PAS with diastase | Distinguishes glycogen (digested) from other PAS-positive material | |
| Congo red | Amyloid | Apple green birefringence under polarised light |
| Ziehl-Neelsen | Acid fast bacilli (mycobacteria) | Red on blue |
| Gram | Bacteria | Gram positive purple, negative pink |
| Masson trichrome | Collagen and fibrosis | Collagen blue or green |
| Perls Prussian blue | Iron (haemosiderin) | Blue |
| Oil red O, Sudan | Lipid; needs frozen section | Red |
| Silver stains | Reticulin, fungi, spirochaetes, neurofibrillary tangles | Black |
| Alcian blue | Acid mucins | Blue |
| Toluidine blue | Mast cell granules (metachromasia) | Purple |
Basophilic structures (nuclei, ribosomes, rough endoplasmic reticulum) bind the basic dye haematoxylin and appear blue; eosinophilic (acidophilic) structures such as cytoplasmic protein, collagen and red cells appear pink.
Congo red with apple green birefringence remains the definitive test for amyloid, and requires polarised light.