Cardiac Amyloidosis - X

Congo red birefringence of cardiac amyloid.  A.  Congo red stain shows “congophilic” deposits upon bright field light microscopy.  (Congo red.  (X100) .   B. Examination of the same section under polarized light microcopy shows birefringent collagen in white and “apple green” birefringent amyloid deposits corresponding to the congophilic material in A.  (Congo red, polarized light.  X100).

The Congo red stain can be examined with polarized visible light microscopy or with ultraviolet (fluorescence) microscopy. This is helpful to detect incidental minute amounts of amyloid in valvular structures.thioflavins (S or T) are very sensitive and unambiguous stains to detect amyloid.