Diffuse large B-cell lymphoma presenting with cardiac tamponade and complete heart block

Diffuse large B-cell lymphoma (DLBCL) frequently presents with disseminated disease, and clinically evident cardiac involvement is rare and challenging to manage. A 51-year-old woman presented with complete heart block (CHB) and hemodynamically significant cardiac tamponade requiring urgent pericardiocentesis. Multimodality imaging showed a large right atrial mass with diffuse cardiac infiltration and disseminated intra-abdominal disease, complicating pacing access, rhythm control, and anticoagulation decisions. Computed tomography-guided adrenal biopsy confirmed DLBCL and chemotherapy with rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone was commenced, resulting in resolution of the CHB, marked reduction in tumor burden and sustained resolution of the pericardial effusion within the following weeks. Learning objective Key learning points include the central role of tissue diagnosis to guide therapy and prognostication in diffuse malignancy, the potential reversibility of conduction disease with chemotherapy initiation in diffuse large B-cell lymphoma and the complementary strengths of multimodality imaging in complex cardiac disease.