An unusual “mass” within the left atrium: Localized aneurysm of a patent foramen ovale tunnel

Masses on the interatrial septum are usually caused by myxomas or thrombi within a patent foramen ovale. We report a 53‐year‐old male patient with a hollow mass within the left atrium that was incidentally found during a routine transthoracic echocardiography. Further investigation of the mass with transesophageal two‐ and three‐dimensional echocardiography has revealed that the mass was a localized aneurysm of a patent foramen ovale tunnel. While aneurysms of interatrial septum are relatively common in normal population, to the best of our knowledge, present case is the first report of a localized aneursym of a patent foramen ovale tunnel.