PAS staining is mainly used for staining structures containing a high proportion of
carbohydrate macromolecules (
glycogen,
glycoprotein,
proteoglycans), typically found in e.g.
connective tissues,
mucus, the
glycocalyx, and
basal laminae. PAS staining can be used to assist in the diagnosis of several medical conditions: •
Glycogen storage disease (versus other storage disorders). •
Adenocarcinomas, which often secrete neutral mucins. •
Paget disease of the breast. •
Alveolar soft part sarcoma. • Staining
macrophages in
Whipple's disease. • It can be used to diagnose
α1-antitrypsin deficiency if periportal liver hepatocytes stain positive. • Aggregates of PAS-positive lymphocytes are present in epidermis in
Mycosis fungoides and
Sézary syndrome, called Pautrier microabscesses. •
Ewing sarcoma •
Erythroleukemia, a leukemia of immature red blood cells. These cells stain a bright fuchsia. •
Pulmonary alveolar proteinosis. •
Fungal infection, the cell walls of fungi stain magenta; this only works on living fungi. In contrast,
Grocott's methenamine silver stain (GMS) will stain both living and dead fungal organisms. • It is used to identify glycogen in lung biopsy specimens of infants with pulmonary interstitial glycogenosis (PIG). • It can be used to highlight super cross-linked lipids inclusions in
ceroid lipofuscinosis (NCL). 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 that has been treated with diastase will lack any positive PAS staining in those locations on the slide PAS staining is also used for staining
cellulose. One example would be looking for implanted medical devices composed of nonoxidized cellulose. If the PAS stain will be performed on tissue, the recommended
fixative is
10% neutral-buffered formalin or
Bouin solution. For
blood smears, the recommended fixative is
methanol.
Glutaraldehyde is not recommended because free
aldehyde groups may be available to react with the
Schiff reagent, which may result in
false positive staining. == See also ==