light microscopic appearance of amyloid
Without staining, amyloid appears as a homogeneous, amorphous, hyaline extracellular material. It is eosinophilic when stained with hematoxylin–eosin and metachromatic with crystal violet. Amyloid stains homogeneously with Congo red (congophilic) as a result of its β-pleated sheet configuration. Viewing of Congo red-stained tissue under polarized microscopy yields the pathognomonic apple green birefringence.
