Giant Left Atrial Appendage Mimicking a Mediastinal Tumor.

A 22-year-old man visited our hospital for an evaluation of a suspected mediastinal tumor on chest radiography (Picture A, arrow). He was asymptomatic and had no past medical history. Electrocardiography (ECG) and transthoracic echocardiography demonstrated normal findings, and Holter ECG showed no significant arrhythmias. As contrastenhanced three-dimensional chest computed tomography revealed an upwardly-enlarged left atrial appendage (LAA), without any other abnormalities (Picture B, arrows), a congenitally giant LAA was diagnosed. Transesophageal echocardiography showed no thrombi or spontaneous echo contrast in the LAA (Picture C, arrows), with a normal LAA emptying velocity (Picture D). Therefore, we did not prescribe any anti-coagulant agents or recommend surgical resection. A giant LAA is a rare anomaly, either congenital or ac-