ABSTRACT
We report a case of myxoid sarcoma in the left atrium, which was diagnosed as benign myxoma on preoperative echocardiography. At operation, semisolid mobile masses were found that attached with broad stalk to the posterior left atrial wall and that invaded into the left pulmonary vein and the anterior mitral leaflet. The patient underwent excision of left atrial tumor masses, mitral valve replacement, and left pneumonectomy. The histological diagnosis was undifferentiated cardiac myxoid sarcoma. Although echocardiography lead to the choice of diagnostic test of intra-atrial tumor, magnetic resonance imaging, computed tomography, and intraoperative transesophageal echocardiography may be needed for differential diagnosis, with indeterminate malignant findings on preoperative transthoracic echocardiography. Anesthesiologists are often confronted with cases that are unusual, therefore preoperative understanding of the cases are important for safe anesthetic management.