Multi-chamber Intracardiac Extension and Embolic Stroke: A Rare Complication of Mediastinal Non-seminomatous Germ Cell Tumor.

Primary mediastinal non-seminomatous germ cell tumors (PMNSGCT) are aggressive malignancies. A rare and high-risk complication is the extension of the tumor into the cardiac chambers or the formation of tumor-associated thrombi, which carry a profound risk of systemic or pulmonary embolization. We present a complex case of a 21-year-old man with superior vena cava obstruction (SVCO) and massive, multi-chamber intracardiac tumor extension discovered incidentally following a presentation of chest pain and ST-segment elevation. He was found to have a pericardial effusion that later progressed to impending tamponade. Transesophageal echocardiography (TEE) revealed highly mobile masses within the right atrium (RA), right ventricle (RV), and left atrium (LA), the latter originating from the pulmonary veins.  The clinical course was complicated by embolic cerebral infarcts. Despite the high risk of further embolization, the patient was managed with emergent pericardiocentesis, therapeutic anticoagulation, and VIP (Etoposide, Ifosfamide, Cisplatin) chemotherapy protocol. The patient achieved complete resolution of the intracardiac masses, demonstrating the efficacy of the "chemotherapy-first" medical debulking approach in managing high-risk inoperable intracardiac tumor burden. This case highlights the important role of echocardiography in intracardiac tumor diagnosis and the clinical challenge of distinguishing tumor thrombus from direct extension. It demonstrates the efficacy of a chemotherapy-first approach in managing high-risk or inoperable intracardiac tumor burden.