Left atrial appendage mass: is it always a thrombus?

Myxoma is the most common benign tumor of the heart, but it is very rare for it to originate from the left atrial appendage. Distinguishing between a mass, a thrombus, and a tumor in the body of the left atrium with preoperative transthoracic or transesophageal echocardiography is very difficult, even more so in patients with mitral valve disease and chronic atrial fibrillation. A 50-year-old male patient was admitted for surgery with the diagnosis of mitral stenosis and chronic atrial fibrillation. Transesophageal echocardiography demonstrated a mass attached to the wall of the left atrial appendage. Histopathological examination of the mass showed an image compatible with a myxoma. We hereby describe a case of a left atrial appendage myxoma mimicking a left atrial appendage thrombus.