An 83-year-old woman presented with a new onset of dyspnea and dysphonia. Physical examination revealed no abnormalities. Computerized tomography, bidimensional echocardiography, and cardiac magnetic resonance confirmed the presence of a cardiac mass in the left atrium. Surgical resection was uneventful and showed the origin of the mass in the ostium of the left inferior pulmonary vein. Histological evaluation revealed undifferentiated pleomorphic sarcoma with myxoid features. This case highlights the importance of considering cardiac neoplasms as a rare differential diagnosis, including rare and misleading clinical presentations.