Stains & CD markers
Mucins
Copyright: 2002-2024, PathologyOutlines.com, Inc.
PubMed Search: Mucins
Mucins
Author: Nat Pernick, M.D.
Last author update: 1 June 2005
Last staff update: 11 September 2023
Copyright: 2002-2024, PathologyOutlines.com, Inc.
PubMed Search: Mucins
Table of Contents
Definition / general | Terminology | Uses by pathologists | Microscopic (histologic) images | Additional referencesCite this page: Pernick N. Mucins. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/stainsmucins.html. Accessed December 3rd, 2024.
Definition / general
- 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)
- Membrane bound mucins at locus 7q22, 3q and 1q21 (MUC1, MUC3A, MUC3B, MUC4, MUC12, MUC13, MUC17)
Terminology
- Mucin types include acid mucins and neutral mucins
- Acid mucins:
- 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
- Acid-simple non-sulfated:
- 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
Uses by pathologists
- Mucin stains:
- 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
- Atain 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
- Alcian blue:
Microscopic (histologic) images
Contributed by Andrey Bychkov, M.D., Ph.D.
PAS staining of thyroid
Mucicarmine staining
Additional references
