Diagnosis of Amyloid Using Congo Red

  • Alexander J. HowieEmail author
Part of the Current Clinical Pathology book series (CCPATH)


Congo red is the accepted standard for detection of amyloid. Detection is easier on sections thicker than usual. A simple and convenient method is that described by Stokes. Between crossed polariser and analyser, the red colour of amyloid stained by Congo red is changed to a variety of other colours, called anomalous colours. These can be explained by the principles of optical physics. Only green is usually reported, because this colour is widely but not entirely correctly assumed to be essential for the diagnosis, but this idea is based on a misunderstanding of the physics. Combinations such as green and yellow or even blue and yellow are more commonly seen than green on its own. Other combinations of anomalous colours appear when the polariser and analyser are progressively uncrossed. All these colours are genuine, respectable and helpful findings, not artefacts or technical errors to be ignored. The changes in colour are a useful way to confirm amyloid.


Amyloid Anomalous colours Congo red Polarisation microscopy 


  1. 1.
    Bennhold H. Eine spezifische Amyloidfärbung mit Kongorot (a specific staining of amyloid with Congo red). Münch Med Woch. 1922;69:1537–8.Google Scholar
  2. 2.
    Bennhold H. Über die Ausscheidung intravenös einverleibten Kongorotes bei den verschiedensten Erkrangungen insbesondere bei Amyloidosis (on the elimination of intravenously absorbed Congo red in various diseases, in particular in amyloidosis). Deut Arch Klin Med. 1923;142:32–46.Google Scholar
  3. 3.
    Howie AJ, Brewer DB. Optical properties of amyloid stained by Congo red: history and mechanisms. Micron. 2009;40:285–301.CrossRefPubMedGoogle Scholar
  4. 4.
    Aterman K. A pretty a vista reaction for tissues with amyloid degeneration. 1875: an important year for pathology. J Hist Med. 1976;31:431–47.Google Scholar
  5. 5.
    Aterman K. A historical note on the iodine-sulphuric acid reaction of amyloid. Histochemistry. 1976;49:131–43.CrossRefPubMedGoogle Scholar
  6. 6.
    Horobin RW, Kiernan JA. Conn’s biological stains. 10th ed. Oxford: BIOS Scientific; 2002. p. 132–4.Google Scholar
  7. 7.
    Puchtler H, Sweat F, Levine M. On the binding of Congo red by amyloid. J Histochem Cytochem. 1962;10:355–64.CrossRefGoogle Scholar
  8. 8.
    Stokes G. An improved Congo red method for amyloid. Med Lab Sci. 1976;33:79–80.PubMedGoogle Scholar
  9. 9.
    Wright JR, Calkins E, Humphrey RL. Potassium permanganate reaction in amyloidosis: a histologic method to assist in differentiating forms of this disease. Lab Invest. 1977;36:274–81.PubMedGoogle Scholar
  10. 10.
    Howie AJ, Brewer DB, Howell D, Jones AP. Physical basis of colors seen in Congo red-stained amyloid in polarized light. Lab Invest. 2008;88:232–42.CrossRefPubMedGoogle Scholar
  11. 11.
    Howie AJ, Owen-Casey MP. Discrepancies between descriptions and illustrations of colours in Congo red-stained amyloid, and explanation of discrepant colours. Amyloid. 2010;17:109–17.CrossRefPubMedGoogle Scholar
  12. 12.
    Heller H, Missmahl HP, Sohar E, Gafni J. Amyloidosis: its differentiation into peri-reticulin and peri-collagen types. J Pathol Bacteriol. 1964;88:15–34.CrossRefPubMedGoogle Scholar
  13. 13.
    Picken MM. Generic diagnosis of amyloid: a summary of current recommendations and the editorial comments on chapters 13–16. In: Picken MM, Herrera GA, Dogan A, editors. Amyloid and related disorders: surgical pathology and clinical correlations. New York: Springer; 2015.Google Scholar

Copyright information

© Springer International Publishing Switzerland 2015

Authors and Affiliations

  1. 1.Department of PathologyUniversity College LondonLondonUK

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