Abstract
Diffuse large B-cell lymphoma (DLBCL) is the most prevalent histologic subtype of non-Hodgkin lymphomas. It usually presents with nodal involvement (cervical, mediastinal, or abdominal), but approximately 30% of patients will exhibit extranodal involvement, with 2-4% presenting as a primary cardiac mass. Multimodal imaging is essential to distinguish these masses from other common benign lesions and to assist in surgical planning. Here, we report a case of DLBCL manifested as a right atrial mass, pericardial effusion, and cardiac tamponade. Transesophageal echocardiogram (TEE) and cardiac magnetic resonance imaging (CMR) were complementary to transthoracic echocardiogram in diagnosing the cardiac neoplasm, with positron emission tomography (PET-CT) aiding in staging and localizing the primary tumor. Biopsy of the cardiac mass or extracardiac involvement confirms the histopathological subtype and guides the treatment. Although primary and secondary cardiac tumors have poor outcomes, early diagnosis and aggressive treatment can influence prognosis.