H&E Stain vs. PAS Stain — What's the Difference?

Hematoxylin and Eosin (H&E) staining is a fundamental technique in histology and pathology, providing a broad overview of tissue architecture and morphology. Hematoxylin stains cell nuclei blue, delineating them clearly against the pink cytoplasmic and extracellular matrix background stained by eosin. This dual staining offers a contrast that is invaluable for examining cell and tissue structure, enabling the identification of various cell types and the overall layout of tissue specimens.

The Periodic Acid-Schiff (PAS) stain, on the other hand, is specialized for identifying structures rich in carbohydrates. By oxidizing polysaccharides to aldehydes, which then react with Schiff's reagent to produce a magenta color, PAS staining highlights components like glycogen, mucins, and basement membranes. This makes it particularly useful for diagnosing diseases where these elements are involved, such as glycogen storage diseases, certain fungal infections, and components of the extracellular matrix.

H&E is essential for general histopathological assessment, providing a quick and comprehensive view of tissue health and basic structures, whie PAS offers more specialized insights. It is especially valuable in highlighting details that are not readily apparent with H&E, such as the basement membrane in kidney biopsies, which is crucial for diagnosing conditions like Alport syndrome or diagnosing fungal infections where the cell wall components are visualized.

The choice between H&E and PAS staining depends on the diagnostic needs. H&E is suitable for routine examination and is often the first step in tissue analysis. If further detail on carbohydrate structures is required, or if there is a need to highlight specific components like fungi or basement membranes, PAS staining is employed. In many diagnostic processes, both staining methods may be used in sequence to provide a comprehensive understanding of the tissue pathology.