Malignant Right Atrial Mass With Inferior Vena Cava Extension Presenting as Budd-Chiari Syndrome: A Multimodality Imaging Case Report.

A 29-year-old man with no significant past medical history presented with progressive abdominal pain, ascites, and New York Heart Association (NYHA) class III exertional dyspnea. Clinical evaluation suggested portal hypertension, and imaging confirmed extensive inferior vena cava and hepatic vein thrombosis consistent with Budd-Chiari syndrome. Transthoracic echocardiography revealed a large right atrial mass extending from the inferior vena cava, raising suspicion for a malignant cardiac tumor. Cardiac magnetic resonance imaging (MRI) and computed tomography (CT) further characterized the lesion with features of malignancy, without evidence of extra-cardiac primary disease. Coronary angiography unexpectedly demonstrated chronic right coronary artery occlusion with well-developed collateral circulation. Laboratory investigations excluded common thrombophilic and autoimmune causes of venous thrombosis. The patient was initiated on anticoagulation and supportive therapy; however, rapid clinical deterioration precluded surgical resection.  This case highlights a rare presentation of malignant right atrial tumor manifesting as Budd-Chiari syndrome in a young patient. It emphasizes the diagnostic value of multimodality imaging and the need for early recognition and multidisciplinary decision-making in managing such highly lethal conditions.