Endomyocardial biopsy with co-localization of a lymphoplasmacytic lymphoma and AL amyloidosis

Abstract

In about 4% of cases, amyloid light chain (AL) amyloidosis is due to an underlying lymphoplasmacytic lymphoma (LPL) or other monoclonal protein forming low-grade B-cell lymphoma, instead of a plasma cell neoplasm. We report an unusual case of a 55-year-old male with co-localization of an IgG positive LPL and AL amyloidosis in his endomyocardial biopsy (EMB). The patient was diagnosed 4 years earlier with a low grade B-cell non Hodgkin lymphoma stage IV, at the time classified as marginal zone lymphoma. He received several lines of treatment for his lymphoma, which had shown progressive disease. Four years after initial diagnosis, he developed increasing dyspnea on exertion. Echocardiography demonstrated left and right ventricular hypertrophy with classical apical sparing, suspicious for cardiac amyloidosis. Bone marrow biopsy revealed massive infiltration by his low grade B-cell lymphoma, which was now reclassified as LPL based on the demonstration of a MYD88 L265P mutation. An EMB confirmed the presence of amyloid, which was typed as AL amyloidosis by the use of immunoelectron microscopy. In addition, mild B-cell infiltrates were present in the EMB, which were shown to be part of his LPL by the demonstration of the MYD88 L265P mutation using the highly sensitive droplet digital polymerase chain reaction technique. This is a rare case of cardiac AL amyloidosis based on an IgG kappa positive LPL, in which not only the amyloid but also the lymphoma itself were present in the EMB. In addition, this case nicely illustrates the use of 2 highly sensitive techniques (immunoelectron microscopy and droplet digital polymerase chain reaction), which both can be performed on small, formalin-fixed paraffin-embedded biopsies.