Congo red stain for amyloid. This cardiac section shows a light microscopic image of the stain for amyloid using Congo red stain in a case of primary amyloidosis.
Congo red stain for amyloid, polarized light. The same stain as in IX.G.001, under polarized light, shows characteristic apple-green birefringence of amyloid protein deposits in the heart, which is a correlate of a beta-pleated sheet structure of the amyloid protein on ultrastructural analysis.
Amyloidosis. Marrow biopsy of a 44 year old woman who presented with lower leg edema and marked proteinuria. Renal biopsy showed glomerular lesions with mesangial infiltrations of amorphous material. Special stains, electron microscopy and fibril width measurements (<10 angstroms) were compatible with amyloidosis. Marrow examination did not show an increase in plasma cells and the plasma cells were not monoclonal by immunostain but she had a marked increase in the serum kappa to lambda light chain ratio. (A) Marrow vessel in center of field stained with H & E, showing amorphous infiltrate in vessel wall. (B) Congo red staining of a vessel displaying birefringence (apple green color) under polarized light, characteristic of amyloid deposition.