Inflammatory pseudotumour originating from congenital double atrial septum

A 60-year-old man who had undergone radiofrequency catheter ablation (RFCA) for recurrent symptomatic atrial fibrillation twice, the last of which was 12 years ago, presented to our outpatient clinic with an incidental cardiac mass. Vital signs were stable without fever and blood test results were normal. Previous transoesophageal echocardiography (TEE) performed before RFCA had revealed a double interatrial septum with an atrial septal aneurysm (Panel A) and computed tomography (CT) also showed a double atrial septum with a deviation of the septum premium and atrial septal aneurysm (Panel B). On the current visit, we observed on transthotacic echocardiography a hypoechogenic mass on the interatrial septum adjacent to the posterior left atrium. TEE revealed a round, heterogeneous hypoechogenic mass measuring 3.2×3.1 cm filling the space between the two atrial septa (Panels C and F). CT also showed a low attenuated mass (Panel D), and magnetic resonance imaging revealed a well-defined lobulated mass (3 cm) without definite enhancement (Panel E). Likely diagnosis was a cardiac tumour. Surgical mass excision was planned, however, at the time of surgery, what was thought to be a mass turned out to be a large amount of sticky greenish pus-like substance. Histopathology showed only normal heart tissues and cultures showed no growth. The mass was determined to be an inflammatory pseudotumour resulting from infection or inflammation potentially associated with a previous interatrial septal puncture during RFCA. Postoperative follow-up echocardiography revealed no residual cardiac mass or complications. The patient was discharged and followed up at an outpatient clinic without complications. Data availability: The data underlying this article will be shared on reasonable request to the corresponding author.