Lipomatous hypertrophy of the inter-atrial septum: FDG PET/CT appearance and clinical correlation

Objectives: 1. To gain an understanding of how incidental findings are part of the appropriate study interpretation. 2. To recognize this uncommon finding when seen on FDG PET/ CT. 3. To avoid false positive diagnosis of a cardiac related lesion. 4. To understand how to interpret this finding and direct further investigation if needed. Abstract: Positron emission tomography/computed tomography (PET/CT) with 2-[fluorine 18] fluoro-2-deoxy-d-glucose (FDG) has been used in a wide variety of cancer detection and staging. While most of nuclear medicine physicians are familiar with normal physiologic pattern of myocardial FDG uptake, uptake in lipomatous hypertrophy of the inter-atrial septum (LHIS) is uncommon. Incidence of LHIS is 1% in autopsy studies but up to 8% in transthoracic echocardiography. When present, LHIS may present with variable degree of FDG uptake mimicking malignancy. However, incidence of FDG avid LHIS in patients undergoing PET/CT is not well-established. Therefore, it is of utmost importance to differentiate LHIS from other types of cardiac uptake related to primary cardiac tumors, metastasis or adjacent hypermetabolic nodal disease. Reading physicians should be familiar with this benign finding to avoid false positive interpretations. This review will demonstrate several cases showing FDG uptake in LHIS which needs to be considered in the interpretation and possible impact on clinical management. In addition, we will demonstrate variable degrees and patterns of FDG uptake that could be seen in LHIS of the same patient. We will also show the appearance of some of these findings by other imaging modalities for further characterization.