Periodic acid-Schiff stain

Gastric signet ring cell carcinoma histopatholgy, PAS stain.

Esophageal candidiasis, PAS stain.

Periodic acid-Schiff (PAS) is a staining method used in histology and pathology. This method is primarily used to identify glycogen in tissues. The reaction of periodic acid selectively oxidizes the glucose residues, creates aldehydes that react with the Schiff reagent and creates a purple-magenta color. A suitable basic stain is often used as a counterstain.

Uses

PAS staining is mainly used for staining structures containing a high proportion of carbohydrate macromolecules (glycogen, glycoprotein, proteoglycans), typically found in eg. connective tissues, mucus, and basal laminae.

PAS staining can be used to distinguish between different types of glycogen storage disease. However, it has uses beyond this, such as being indicative of certain forms of cancer, such as Paget's disease, or in staining macrophages in Whipple's disease. It can also be used to diagnose α1-antitrypsin deficiency if periportal liver hepatocytes stain positive.

Presence of glycogen can be confirmed on a section of tissue by using diastase to digest the glycogen from a section, then comparing a diastase digested PAS section with a normal PAS section. The diastase negative slide will show a magenta staining where glycogen is present within a section of tissue, the slide which has been treated with diastase will lack any positive PAS staining in those locations on the slide

The PAS stain is also used to identify erythroleukemia, a leukemia of immature red blood cells. These cells stain a bright fuchsia.^{[1]http://www.answers.com/topic/leukemia-stains-1}

PAS staining is also used for staining cellulose. One example would be looking for implanted medical devices composed of nonoxidezed cellulose.

See also

• PAS diastase
• [1]

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