Reviewer: Nat Pernick, M.D. (see Reviewers page)
Revised: 29 September 2013, last major update June 2005
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.
PubMed Search: Mucins[title]
Mucin types include acid mucins and neutral mucins
- Also called mucopolysaccharides; major glycoprotein components of mucus under normal circumstances
- Large, highly glycosylated proteins with repeat tandem domains rich in serine and threonine sites for O-glycosylation; also contain glyco-conjugates [mucoproteins, glycoproteins, glycosaminoglycans, glycolipids] with high content of sialic acid [N-acyl derivative of neuraminic acid] or sulfated polysaccharide
- Neuraminic acid is a 9 carbon amino sugar derived from mannosamine and pyruvate
- Mucin stains highlight carbohydrate portion of glycoproteins, not the protein component
- Best pan mucin combination may be PAS and Alcian blue
- MUC - epithelial mucins, share a common characteristic of an elevated number of sequences repeated in tandem, that are different for each MUC
- Two main families of MUC genes – gel forming / secreted mucins at locus 11p15 (MUC2, MUC5AC, MUC5B, MUC6) and membrane-bound mucins at locus 7q22, 3q and 1q21 (MUC1, MUC3A, MUC3B, MUC4, MUC12, MUC13, MUC17)
- Acid mucins: simple non-sulfated, simple mesenchymal, complex sulfated and complex connective tissue types
- Acid-simple non-sulfated: contain sialic acid, found in epithelium (gallbladder [benign, adenocarcinoma], intestinal metaplasia in stomach); positive for PAS, Alcian blue at pH 2.5, colloidal iron, and metachromatic dyes. They resist hyaluronidase digestion.
- Acid-simple mesenchymal: contain hyaluronic acid and digest with hyaluronic acid, found in tissue stroma and sarcomas. Positive for Alcian blue at pH 2.5, colloidal iron, and metachromatic dyes; negative for PAS.
- Acid-complex sulfated: found in adenocarcinomas; usually positive for PAS, Alcian blue at pH 1, colloidal iron, mucicarmine, and metachromatic stains. They resist hyaluronidase digestion
- Acid-complex connective tissue: found in tissue stroma, cartilage, and bone; includes chondroitin sulfate, keratan sulfate; positive for Alcian blue at pH 0.5; negative for PAS
- Neutral mucins: GI tract, prostate; stain with PAS only (negative for Alcian blue, colloidal iron, mucicarmine, or metachromatic dyes); note that thyroglobulin and other neutral glycoproteins are also PAS positive
- Alcian blue: stains acid-simple non-sulfated and acid-simple mesenchymal mucins at pH 2.5, acid-complex sulfated mucins at pH 1.0 and acid-complex connective tissue mucins at pH 0.5; does NOT stain neutral mucins
- Colloidal iron: stains acid-simple non-sulfated, acid-simple mesenchymal, acid-complex sulfated mucins. Does NOT stain neutral mucins or acid-complex connective tissue mucins; theory: acid mucopolysaccharides attract iron particles stabilized in ammonia and glycerin; requires formalin fixation; false positives include phospholipids and free nucleic acids; more specific if hyaluronidase pre-digestion; for chromophobe carcinomas, have diffuse strong staining with reticular pattern
- Mucicarmine: Very specific for epithelial mucins, including adenocarcinomas; although insensitive; stain contains carmine (red coloring material) and aluminum chloride
- PAS (periodic acid-Schiff): stains glycogen as well as mucins, but tissue can be pre-digested with diastase to remove glycogen; stains neutral and acid-simple non-sulfated and acid-complex sulfated mucins; does NOT stain acid-simple mesenchymal mucins and acid-complex connective tissue mucins
End of Stains > Mucins
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