Clinically atypical abdominal manifestation of the lipoma localized in the right atrium: "Invagination hypothesis" revisited.

Cardiac lipomas are the second most common cardiac tumors. They are usually asymptomatic and diagnosed as incidental findings. We describe a 71-year-old patient with a tumor in the right atrium. In echocardiography and MRI scan, the diagnosis of a cardiac lipoma was suspected. Moreover, MRI demonstrated continuity of pericardial fat and the tumor in the right atrium by infolding of the atrial wall and epicardial adipose tissue in the space between the atrial walls, which might be a hint for the Waterstone groove hypothesis. An operative resection was performed which confirmed the suspected diagnosis.