Lipomatous hypertrophy of the interatrial septum is an incidental finding, usually asymptomatic and does not require any treatment. It is defined as a thickening of the interatrial septum of >20 mm thickness with fat attenuation sparing fossa ovalis 1. It is commonly seen in elderly obese patients and may be associated with corticosteroid therapy. If unaware of this condition this might be misinterpreted as thrombus or malignancy. Differential diagnosis includes cardiac lipoma.