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.

在大约 4% 的病例中，淀粉样蛋白轻链 (AL) 淀粉样变性是由于潜在的淋巴浆细胞淋巴瘤 (LPL) 或其他单克隆蛋白形成的低级别 B 细胞淋巴瘤，而不是浆细胞肿瘤。我们报告了一个不寻常的病例，一名 55 岁男性在其心内膜心肌活检 (EMB) 中同时存在 IgG 阳性 LPL 和 AL 淀粉样变性。该患者在 4 年前被诊断为低级别 B 细胞非霍奇金淋巴瘤 IV 期，当时被归类为边缘区淋巴瘤。他的淋巴瘤已经显示出进行性进展，他接受了几线治疗。初次诊断四年后，他在劳累时出现加重的呼吸困难。超声心动图显示左心室和右心室肥厚，典型心尖保留，怀疑心脏淀粉样变。MYD88 L265P 突变。EMB 证实存在淀粉样蛋白，通过使用免疫电子显微镜将其分类为 AL 淀粉样变性。此外，EMB 中存在轻度 B 细胞浸润，通过使用高度敏感的液滴数字聚合酶链反应技术证明MYD88 L265P 突变，这被证明是他的 LPL 的一部分。这是一种罕见的基于 IgG kappa 阳性 LPL 的心脏 AL 淀粉样变性病例，其中 EMB 中不仅存在淀粉样蛋白，而且还存在淋巴瘤本身。此外，这个案例很好地说明了 2 种高度敏感的技术（免疫电子显微镜和液滴数字聚合酶链反应）的使用，这两种技术都可以在小的、福尔马林固定的石蜡包埋活检组织上进​​行。