Intensely Hypermetabolic Lipomatous Hypertrophy of the Interatrial Septum on 18-FDG PET With MRI and CT Correlation

Abstract

We present a 69-year-old female patient with a history of emphysema, rosacea, and breast cancer. The patient was in remission for 4 years until a 15-pound weight loss prompted further evaluation with a computed tomography of the chest, abdomen, and pelvis, cardiac magnetic resonance imaging, as well as an 18-FDG-PET scan to evaluate for metastatic disease and potential cardiac abnormalities. There was an intensely hypermetabolic bilobed focus within the region of the interatrial septum, correlating with the patient's lipomatous hypertrophy of the interatrial septum (LHIS), which was identified on computed tomography and magnetic resonance imaging. LHIS is a relatively uncommon cardiac finding characterized by excessive deposition of adipocytes with varying quantities of brown fat. Brown fat in LHIS may be hypermetabolic on 18-FDG-PET examinations, and familiarity with the prevalence and features of LHIS will avoid misdiagnosis of metastatic disease.