Occult cardiac diffuse large B-cell lymphoma masquerading as electrical storm and diagnosed after urgent heart transplantation: a rare case report

Background Cardiac lymphoma is rare, frequently mimics inflammatory or infiltrative cardiomyopathy, and can present with malignant ventricular arrhythmias. Occult malignancy discovered only after heart transplantation (HTx) creates a difficult and potentially catastrophic clinical scenario. Case summary A 46-year-old woman presented after about 20 days of cough, dyspnea, chest tightness, moderate pericardial effusion, corrected QT interval (QTc) prolongation, torsades de pointes/ventricular tachycardia (VT), and cardiac arrest. Coronary computed tomography angiography (CTA) showed no significant stenosis. Pericardial fluid was lymphocyte-predominant with high adenosine deaminase (ADA), but sputum testing, GeneXpert and next-generation sequencing (NGS) were negative. Recurrent VT progressed despite antiarrhythmic therapy, electrolyte correction, cardioversion, ventilation, vasopressors, and continuous renal replacement therapy (CRRT). Echocardiography later suggested arrhythmogenic right ventricular cardiomyopathy (ARVC). Because of refractory electrical storm, cardiogenic shock, lactic acidosis, and liver–renal dysfunction, venoarterial extracorporeal membrane oxygenation (VA-ECMO) was instituted, and urgent HTx was performed. Explant pathology unexpectedly revealed extensive non-germinal-centre B-cell-like (non-GCB) diffuse large B-cell lymphoma (DLBCL) with BCL2/c-Myc double-expression, consistent with systemic DLBCL with extensive cardiac involvement and bone marrow involvement. Post-transplant bone marrow evaluation showed 44.83% abnormal B-lymphocyte infiltration with haemophagocytosis, meeting haemophagocytic lymphohistiocytosis (HLH)-2004 criteria (fever, cytopenias, hyperferritinemia, haemophagocytosis, reduced NK-cell activity). Pancytopenia, infection, cholestasis, bleeding, and acidosis progressed rapidly, and the patient died soon after withdrawal of care. Conclusions This case illustrates both the necessity and danger of emergency HTx for unexplained electrical storm. When haemodynamics permit, aggressive pre-transplant evaluation for occult malignancy should be pursued.