[False mass in the left atrium... or better: true mass in false atrium].

We report the case of a 59-year-old man who underwent transesophageal echocardiography following a cryptogenic minor stroke. An image of a solid mass of the left atrial appendage, highly suggestive of a thrombus, was observed. The patient was treated for 10 weeks with oral anticoagulants. Because of the absence of changes in the echocardiographic appearance of the mass at follow-up, the patient was submitted to surgery. At surgical exploration no endocavitary thrombus was found, but the left atrial appendage appeared hypoplastic and dysmorphic. A biopsy was taken and the left atrial appendage was plicated. To our knowledge, this is the first report of a case of dysmorphism of the left atrial appendage mimicking a left atrial thrombus in a patient with cryptogenic minor stroke.