Abstract
Primary cardiac sarcoma is a rare type of intracardiac mass. This report describes a patient with atrial flutter who had a new right atrial mass incidentally discovered on transesophageal echocardiography. A thrombus was suspected based on radiographic appearance, but there was minimal change with anticoagulation. The mass was resected and found to be an undifferentiated pleomorphic cardiac sarcoma, an uncommon sub-type within the already rare category of primary cardiac neoplasms. This report highlights the importance of considering primary malignancy and thoroughly correlating radiographic and clinical evidence during the diagnostic workup of patients with intracardiac masses.