A large well-circumscribed ovoid-shaped left atrial mass was noted on multiple echocardiographic views (A). Moderate eccentric mitral regurgitant jet and abnormal high-velocity diastolic flow respected the contours of the mass (B, Online Video 1). Transthoracic 3-dimensional echocardiography images were suspicious of an extracardiac mass compressing on the left atrium (C). Oral administration of contrast bubbles with soda water was not able to enhance the mass. A large filling defect that was noted adjacent to the left atrium during first-pass perfusion of gadolinium during magnetic resonance imaging suggested that this was not an artefact (D, Online Video 2). Sagittal T1-weighted spin echo (black blood) images on magnetic resonance imaging demonstrated a T1 iso-intense extracardiac hiatal...