The PAS stain identifies polysaccharides, mucus substances, basement membranes, and some fungi by causing them to appear magenta under the microscope. It works by first using periodic acid to oxidize carbohydrate groups, then exposing the tissue to Schiff's reagent, which causes aldehyde groups produced in the first step to appear magenta. The PAS stain is used to identify conditions involving abnormal glycogen storage or mucus production, such as certain tumors, infections, and genetic diseases. It helps diagnose issues in tissues from the liver, kidney, lung, muscle, and other organs.

1. PAS staining
DR.SUNDARESAN
PATHOLOGY

2. What Does PAS Stain?
 (1) Polysaccharides: The main polysaccharide identified via histology staining in human and
animal tissue sections is glycogen. This is present in numerous tissues, including skeletal
muscle, cardiac muscle, liver, and kidney.
 (2) Neutral mucus substances: These can include glycoproteins, glycolipids, and neutral
mucins, which are produced by epithelial cells in different organs.
 (3) Tissue basement membranes: These PAS-positive thin layers of reticular connective
tissue anchor and support epithelium and endothelium to underlying connective tissue.
 (4) Fungal organisms: The cell walls of some fungal organisms contain high levels of
carbohydrate, and also stain PAS-positive. However, this only works on living fungi.

3. General Principles of the Stain
 The first reaction -periodic acid acting as an oxidising agent to oxidise the carbon-to-carbon bonds
between two hydroxyl groups. This produces Schiff reactive aldehyde groups.
 second reaction- This comprises a mixture of basic fuchsin, hydrochloric acid, and sodium
metabisulphite. The basic fuchsin in the mixture reacts with newly formed aldehyde groups in the tissue to
produce a bright magenta colour.
 Finally, when the section is rinsed in water, bound fuchsin molecules in the tissue then produce a bright magenta
colour.
 Haematoxylin is then typically used as a counter stain to visualise other tissue elements. When PAS is used to
demonstrate fungal organisms, however, a light green counter stain is preferred.

4. PROCEDURE:
 1. Deparaffinize and hydrate to distilled water.
 2. Place slides into 1% Periodic acid for 10 minutes.
 3. Rinse in tap water.
 4. Schiff's Reagent for 15-30 minutes.
 5. Wash in running tap water for 5 minutes.
 6. Counterstain in hematoxylin for 5 minutes.
 7. Wash in tap water, differentiate,blue and wash in distilled water.
 8. Dehydrate in alcohol, clear, and coverslip.

5. Who Uses PAS Stain?
 Glycogen storage diseases: (liver -(hepatocytes, alpha-1-antitrypsin disease,) muscles-
(demonstrate glycogen), or kidney- (renal cell carcinoma ).
 Tumors: Glycogen granules can also be present (pancreas-(acinar cell carcinoma), lung-
(alveolar proteinosis), and bladder).
 Adenocarcinomas, which often secrete neutral mucins.
 Alveolar soft part sarcoma.[2]
 Staining macrophages in Whipple's disease.[3]
 α1-antitrypsin deficiency if periportal liver hepatocytes stain positive.
 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;(

6.  Breast cytology: PASD positive cells with structure and producing nuclear indentation, particularly
in dissociated or atypical cells, correlate with malignant histology.
 Fungi: stains fungal cell walls; PAS+ granule, spores is diagnostic of microsporidia.
 Hematopathology: ALL
 Kidney: renal cell carcinoma (stains glycogen, removed by diastase)
 Liver: routine stain for hepatocytes , alpha-1-antitrypsin disease
 Lung: alveolar proteinosis
 Muscle biopsies: demonstrate glycogen
 Pancreas: acinar cell carcinoma (PASD+)
 Parotid glands: zymogen granules are PAS+
 Prostate: Cowper’s glands are PASD+
 Skin: eosinophilic globoid bodies (Kamino bodies) in Spitz nevus are PASD+
 Small intestine: stains Whipple’s disease bacteria
 Testis: stains intratubular germ cell neoplasia and seminoma (PAS+, PASD negative)
 Tumors: adenocarcinoma of various sites (mucin is PASD+), alveolar soft parts sarcoma (PASD+
crystalline structures), clear cell tumors (stains glycogen), glycogen rich carcinomas, balloon cell
melanoma, granular cell tumor (cytoplasmic granules).

7. Histologic feature
 Glycogen, basement membranes,
mucus substances, fungal organisms.
 Nuclei
 Other tissue elements
Colour with PAS Stain
 Magenta
 Blue (with haematoxylin counter stain)
 Green (with light green counter stain)

8. Periodic Acid – Schiff [PAS]
Reaction
Giant multinucleate late normoblasts (left).
Granular PAS positivity in proerythroblasts
and homogeneous positivity in the later
normoblasts

9. alpha-1-antitrypsin deficiency

10. Diagnosis
moderately differentiated
adenocarcinoma
Description
Dysplastic epithelium with
little mucus formation.

11. granular cell tumor

12. Positive PAS stain acute
megakaryocytic
leukemia AML, M7.
Positive PAS stain in ALL PAS positivity in M6. Not the
intense staining of the large
abnormal erythroblast.