Common special stains used in the histology lab

  Acid Fast Bacteria(AFB) 
Use in
the histological visualization of Acid Fast Bacteria and Tubercle Bacilli. The lipoid capsule of the acid-fast organism takes up carbol fuchsin and resists decolorization.

Acid Fast Oganisms: bright red
Background: blue

  Alcian Blue (pH 2.5)
For the demonstration of acid mucopolysaccharides.

Acid Mucins: blue
Nuclei: red

  Congo Red
Use in the histological visualization of amyloid in tissue sections. Examination under a polarizing microscope results in green birefringence of amyloid.

Amyloid: red to pink
Erythrocytes: light orange
Eosinophil Granules: orange to red
Nuclei: blue

  Colloidal Iron
To demonstrate carboxylated and sulfated mucopolysaccharides and glycoproteins.

Acid Mucopolysaccharides & Sialomucins: bright blue
Nuclei: pink/red
Cytoplasm: pink

Elastic (Modified Verhoff's)
To demonstrate elastin in tissue sections. Demonstration of elastic is useful in cases of emphysema (atrophy of elastic tissue), arteriosclerosis (thinning and loss of elastic fibers) and various other vascular diseases.

Elastic Fibers: black to blue/black
Nuclei: blue to black
Collagen: red
Muscle & Other: yellow

  Iron (Prussian Blue)
Use in the detection of ferric iron in tissues, blood smears, or bone marrow smears. Ferric iron is normally found in small amounts in bone marrow and the spleen. Abnormally large deposits may be seen in hemochromatosis and hemosiderosis. Ionic iron reacts with acid ferrocyanide producing a blue color.

Iron: bright blue
Nuclei: red
Background: pink

Use in the histological visualization of acid mucopolysaccharides in tissue sections. This stain is useful in distinguishing mucin negative undifferentiated squamous cell lesions from mucin positive adenocarcinomas. In addition, will stain the mucopolysaccharide capsule of Cryptococcus neoform.

Mucin: pink/red
Capsule of Cryptococcus: red
Nuclei: black/blue
Other: yellow

  Grocott's Methenamine Silver(GMS)
Use in the histological visualization of fungi, basement membrane and some opportunistic organisms such as Pneumocystis carinii. Pneumocystis carinii is an opportunistic pathogen that causes severe pulmonary disease in humans, dogs, rats, mice and other vertebrate species with acquired, induced, or inherited immune deficiencey syndromes. In addition, this procedure will demonstrate Actinomyces and related species, Nocardia asteroids and certain encapsulated bacteria.

Fungi, Pneumocystis Carinii: black
Background: green

  Gomori's One Step Trichrome
To identify an increase in collagenous connective tissue fibers, or to differentiate between collagen and smooth muscle fibers

Nuclei: black
Cytoplasm, Keratin, Muscle Fibers: red
Collagen & Mucus: green or blue

  Periodic Acid Schiff (PAS)
Used to demonstrate lymphocytes and mucopolysaccharides. The staining pattern of the lymphocytes are helpful in making therapeutic decisions in established cases of lymphocytic leukemia. PAS staining may also be used for the demonstration of fungal organisms in tissue sections.

PAS Positive Material: magenta
Nuceli: black/blue