Metastatic Sarcomatoid Carcinoma Presenting as a Mobile Biventricular Cardiac Mass Mimicking Ventricular Thrombus.

BACKGROUND: Cardiac metastases are more common than primary cardiac tumors but are often clinically silent and underrecognized. Sarcomatoid carcinomas are aggressive malignancies with high metastatic potential and a propensity for late recurrence. CASE SUMMARY: A 71-year-old man with coronary artery disease and prior bladder cancer presented with abdominal pain and atrial flutter with anterolateral ST-segment elevation. Coronary angiography revealed critical midleft anterior descending artery stenosis requiring drug-eluting stent placement. Transthoracic echocardiography demonstrated severely reduced left ventricular systolic function (ejection fraction 20%-25%) and a large heterogeneous intramural mass involving both ventricular apices with interventricular septal extension and mobile cystic components within the right ventricle. Additional imaging identified soft tissue masses in the rectus sheath and right lower lobe. Biopsy confirmed malignant sarcomatoid carcinoma. Progressive septal thickening and extensive endocardial involvement on repeat echocardiography supported metastatic cardiac infiltration. DISCUSSION: Multimodality imaging and clinicopathologic correlation are essential for distinguishing intracardiac thrombus from malignancy. TAKE-HOME MESSAGE: Intracardiac masses with heterogeneous composition and myocardial infiltration should prompt evaluation for malignancy.