When the Heart Is the Target: Case of Primary Pericardial Diffuse Large B‐Cell Lymphoma Presenting With Tamponade

Diffuse large B-cell lymphoma (DLBCL) is an aggressive malignancy and the most common subtype of non-Hodgkin lymphoma, typically presenting with lymphadenopathy. Pericardial involvement is extremely rare. We report the case of a patient who presented with cough and shortness of breath and was admitted for acute hypoxic respiratory failure. During hospitalization, the patient developed atrial fibrillation with rapid ventricular response (RVR). Transthoracic echocardiography revealed a pericardial effusion, which increased in size on repeat imaging 1 week later. The patient subsequently underwent pericardiocentesis, and cytology of the pericardial fluid confirmed DLBCL, with the pericardium identified as the primary site of involvement. The patient was treated with mini-R-CHOP chemotherapy, resulting in marked clinical improvement.