Amyloid is the eosinophilic amorphous extracellular insoluble misfolded fibrillar protein. It has the beta-fibrillar structure that gives its characteristic staining pattern. On electron microscopy, the amyloid fibril shows non-branching filaments that are specifically arranged as beta-pleated sheet configuration which give their characteristic tinctorial pattern. The deposition of the extracellular amyloid protein in various organs and tissues is known as amyloidosis which may be of systemic amyloidosis or localized amyloidosis. This chapter presents the overall concepts of amyloid and the various stains to demonstrate amyloidosis amyloid material in the histopathology sections. Alkaline Congo red stain is the most commonly used stain of amyloid. Thioflavine T is a very sensitive technique. However, it is not a specific stain for amyloid.
KeywordsAmyloid Beta-fibrillar structure Amyloidosis Congo red stain Thioflavine T
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