Case 115

Cardiac Lipoma

Clinical Features

Cardiac lipoma is an uncommon benign encapsulated tumor that most commonly occurs in the right atrium. It is the second most common benign primary cardiac neoplasm after myxoma. Other locations include the epicardium, endocardium, interatrial septum, and left ventricle. Lipomas may grow into the pericardial space when they arise from the epicardium or into a ventricular chamber when they arise from the endocardium. Lipomas tend to be soft and flexible, and even large tumors may not compress the heart. Patients are usually asymptomatic. If there are symptoms of compression, such as pain or shortness of breath, surgical resection is usually performed.

Imaging Features

On CT, a cardiac lipoma manifests as a homogeneous, low-density mass with negative Hounsfield units (Figs. A and B). There is generally no enhancement, and there are no signs of invasion. MRI sequences with and without fat saturation can be used to show that the mass is composed of fat (Figs. C and D). It is important to differentiate cardiac lipoma from lipomatous hypertrophy of the interatrial septum, which has a bilobed appearance and is unencapsulated. Cardiac lipoma does not have significant fluorodeoxyglucose (FDG) uptake, whereas lipomatous hypertrophy may be FDG avid from associated brown fat.

Associations

Multiple fat-containing masses within myocardium have been described in patients with tuberous sclerosis. Current pathologic literature suggests these fatty lesions may represent unencapsulated fat cells rather than true encapsulated cardiac lipomas.