A 76-year old obese woman with a body mass index (BMI) of 36.8 was referred for evaluation of an intracardiac mass, incidentally detected with computed tomography (CT). The CT scan showed massive thickening of the intra-atrial septum with the septal tissue clearly hypointense to normal myocardium and isointense to subcutaneous fat (Figure 1, A) and sparing of the fossa ovalis (Figure 1, B, arrows). Cardiac magnetic resonance imaging confirmed septal thickening of either side of the foramen ovale (Figure 1, C, arrows), being isointense to the subcutaneous fat. Echocardiographic studies (Figure 1, D) revealed hypertrophy of the atrial septum with bright echogenicity of the thickened tissue and