Histological staining is essential for identifying various biochemical components in tissues. Special stains are used to highlight specific macromolecules, aiding in the diagnosis of diseases and tissue abnormalities.
Carbohydrate Stains
Carbohydrates, including glycogen, mucins, and glycoproteins, can be demonstrated using special stains:
- Periodic Acid-Schiff (PAS): Stains glycogen, mucins, and basement membranes magenta.
- Alcian Blue: Identifies acid mucins by staining them blue.
- PAS and Alcian Blue Combination: Differentiates between neutral and acidic mucins.
- Mucicarmine: Selectively stains epithelial mucins red.
Protein Stains
Proteins, including amyloid and fibrin, can be visualized using:
- Congo Red: Demonstrates amyloid deposits by showing apple-green birefringence under polarized light.
- Masson’s Trichrome: Differentiates muscle, collagen, and fibrin.
- Van Gieson’s Stain: Stains collagen fibers red and muscle yellow.
Lipid Stains
Lipids require fat-soluble dyes since routine staining techniques remove fats:
- Oil Red O: Stains neutral lipids red in frozen sections.
- Sudan Black: Stains phospholipids and neutral fats black.
- Ferric Haematoxylin: Demonstrates phospholipids and myelin.
Nucleic Acid Stains
Nucleic acids can be stained to differentiate DNA and RNA:
- Feulgen Stain: Specifically stains DNA red.
- Acridine Orange: Fluorescent stain that binds to nucleic acids.
- Methyl Green-Pyronin: Differentiates DNA (green) from RNA (red).
Pigment Stains
Pigments such as hemosiderin, bile, and melanin can be identified using:
- Perls’ Reaction: Demonstrates iron in hemosiderin as blue granules.
- Fouchet’s Stain: Stains bile pigments green.
- Masson-Fontana Method: Demonstrates melanin as black deposits.
- Schmorl’s Stain: Identifies reducing substances like melanin.
Table of Special Stains
The following table summarizes the special stains used for different tissue components:
| Material | Stain |
|---|---|
| Carbohydrate | Periodic acid-Schiff (PAS) Alcian blue PAS and Alcian blue combination Mucicarmine |
| Lipid | Oil red O Sudan black Ferric haematoxylin |
| Nucleic Acid | Feulgen stain Acridine orange Methyl green-pyronin |
| Hemosiderin Pigment | Perls’ reaction |
| Bile Pigment | Fouchet’s stain |
| Melanin | Masson-Fontana method Schmorl’s stain |
Conclusion
Special stains are crucial in histopathology for identifying carbohydrates, proteins, lipids, nucleic acids, and pigments. They provide valuable diagnostic insights, aiding in the understanding of various diseases and tissue structures.
Source: Hystopathology by Pranab Dey, scribd