Amyloid
  • Any of a group of chemically diverse proteins that appears microscopically homogeneous, but is composed of linear nonbranching aggregated fibrils arranged in sheets when seen under the electron microscope; it stains dark brown with iodine, produces a characteristic green birefringence in polarized light after staining with Congo red, is metachromatic with either methyl violet (pink-red) or crystal violet (purple- red), and fluoresces yellow after thioflavine T staining; amyloid occurs characteristically as pathologic extracellular deposits (amyloidosis), especially in association with reticuloendothelial tissue; the chemical nature of the proteinaceous fibrils is dependent upon the underlying disease process.
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