CARDIAC AMYLOIDOSIS FROM THE PATHOLOGIST'S PERSPECTIVE

Amyloidosis is a systemic, yet an uncommon and probably underdiagnosed disorder which may have cardiac manifestations drawing the cardiologist’s attention to its existence.1-3 Endomyocardial biopsy material is then referred to the pathology laboratory, mainly as a means to establish or confirm the clinical diagnosis. Although the disease has four major types of clinical presentation, the histopathological findings are the same. Microscopically, amyloid is deposited in different parts of the heart such as the interstices of the myofibers to endocardium, blood vessel walls, valve structures, and epicardial fat. The SA and AV nodes as well as the bundle branches are also shown to be involved by the deposits. Based on the routine staining methods, amyloid is pale pink in color and looks homogeneous, distributing in the subendocardial tissue and interstitial myocardium thus producing myocyte compression and atrophy. Conventionally, the Congo red staining method reveals the characteristic amyloid material under the polarized light, where the apple-green birefringence is noted. Alcian blue stain, Crystal violet, and thioflavin-T fluorescence are also employed to demonstrate amyloidosis in biopsy samples.