Carcinoma of Unknown Primary Presenting as Large Right Atrial and Ventricular Mass Secondary to Disseminated Tumor Thrombosis

We report a 65-year-old male patient who presented with right heart failure and a large mobile right atrial and ventricular mass on echocardiography. His computed tomography demonstrated bilateral supraclavicular/mediastinal lymphadenopathy, right atrial and ventricular mass with right pulmonary artery segmental embolism, and multiple liver hypodense lesions. His tumor markers were negative. However, fine-needle aspiration cytology of supraclavicular lymph node revealed metastatic carcinoma suggestive of squamous cell carcinoma. He was suspected to have carcinoma of unknown primary origin. This case illustrates a rare presentation of carcinoma of unknown primary origin with disseminated tumor thrombosis primarily manifesting in heart and other sites.