Cardiac Amyloidosis - V

Endocardial amyloid deposits.  A.  Right ventricular endocardium showing subtle deposition of amyloid in the endocardium as well as around small clusters of cardiac myocytes.   (H&E  50).  B.  Adjacent section to the one show in A demonstrates positive transthyretin deposits in the endocardium and scant subjacent myocytes.  (Immunohistochemistry for trasnthyretin.  X50).  C. Choroid plexus is a useful control for transthyretin immunohistochemistry, as this protein is normally found in the cuboidal epithelium of  the choroid plexus. (Immunohistochemistry for transthyretin  X200).  D.  Left atrial endocardium showing the microscopic equivalent of the extensive yellow-ochre plaques seen on gross examination.  The amyloid deposits are extensive eosinophilic plaques present within the endocardium as well as in the subjacent myocardium. (H&E, X50)  E.  The amyloid plaques are distinct from the fibrous tissue (yellow) or the elastic tissue (black) that normally form the left atrial endocardium .  In this stain the amyloid plaques are stained orang-red.  (Movat pentachrome.  X50).  F.  Examination under ultraviolet light shows the amyloid plaques in the endocardium and smaller deposits in the subjacent myocardium, analogous to the images in D and E) (Thioflavin-S, X50). Congo red is another common stain used to identify amyloid.

Isolated atrial amyloid deposits may be very subtle and more common in elderly patients