The presenting symptoms of primary cardiac lymphomas usually mimic other non-neoplastic cardiac conditions and may include chest pain, dyspnea, heart failure, arrhythmias, and pericardial effusion. Right side of the heart is more frequently involved and the tumor is usually centered in the myocardium. Transesophageal echocardiography (TEE) is the imaging modality of choice. Diagnosis can be made by open biopsy, endomyocardial biopsy, or percutaneous biopsy with TEE imaging. Most primary cardiac lymphomas are diffuse large B-cell lymphomas (DLBCL). The example shown here is composed predominantly of centroblasts. The immunophenotypic and genetic features are similar to DLBCLs occurring in other sites.