FDG-PET scintigraphy
Cardiovascular
Case TypeClinical Cases
AuthorsL. Schneider*1, P.A. Poncelet*2, L. Monnier-Cholley3, Y. Menu3
Patient60 years, female
A 60-year-old woman was diagnosed with epidermoid carcinoma of the right palatine tonsil.
A FDG-PET was performed in order to rule out secondary localisations. This examination showed expected high FDG uptake of the right palatine tonsil and a hypermetabolic cardiac mass (Fig. 1-3).
Figure 1: FDG-PET shows a hypermetabolism of the right palatine tonsil and a high FDG uptake of a cardiac mass.
Figure 2: CT-scan showing a spontaneous hypodense mass (mean density: -41HU) of the interatrial septum with sparing of the fossa ovalis.
Figure 3: Fused PET-CT image showing a hypermetabolic mass of the interatrial septum (mean SUV: 8).
Lipomatous hypertrophy of the interatrial septum (LHIS) is a benign infiltration of fat between the myocardial fibres of the atrial septum which spares the fossa ovalis. This condition is estimated to be present in 2-3% [1] of the general population and is classically associated with older age and obesity, but was also reported in association with long-term corticotherapy. [2, 3] Although LHIS is a benign process, it can induce several complications like atrial arrhythmia, obstruction of the superior vena cava, sudden death. It can also be an obstacle for cardiac interventional procedures. [4]
Histologically, LHIS presents as a non-encapsulated mix of mature adipose tissue, brown fat cells, hypertrophied myocytes and fibrous tissue. The fibrous fibres are responsive of a disruption of the myocardial fibres which can lead to electric perturbation and cardiac arrhythmia. [3, 5]
LHIS has a dumbbell appearance on cross-sectional imaging with spontaneous negative density on CT-scan and fat signal on MR. [2, 5] Sparing of the fossa ovalis is a diagnostic sign specific for LHIS when combined with a fat signal/density. [5] LHIS may show the illusion of a pseudo-capsule by the anatomical structures such as the atrial wall itself.
On FDG-PET, LHIS classically presents an increased uptake of FDG which can lead to a misdiagnosis for a malignant tumour. [1, 5] An explanation for this hypermetabolism is the presence of brown fat cells. [5] This theory is subject to controversy [4] and other hypotheses have been proposed such as an inflammatory process. [6]
Differential diagnosis of LHIS includes: primary cardiac tumours (lipoma, liposarcoma, myxoma, rhabdomyoma, lymphoma, fibroma, fibroelastoma, mesothelioma) but also metastasis (frequent with melanoma and leukaemia). [4] Misdiagnosis between LHIS and one of these lesions can lead to wrong therapeutic decisions of capital importance. Hypermetabolism on FDG PET-CT can be found in many of the conditions and is not necessarily a synonym of a malignant lesion.
To conclude, this case aims to raise awareness on the existence of LHIS and its hypermetabolism on FDG-PET in order to avoid wrong diagnosis of malignancy and, consequently, wrong therapy.
[1] Kuester LB, Fischman AJ, Fan CM, Halpern EF, Aquino SL. (2005) Lipomatous hypertrophy of the interatrial septum: Prevalence and features on fusion 18F fluorodeoxyglucose positron emission tomography/CT. Chest 128(6):3888-3893. (PMID: 16354859)
[2] Heyer CM, Kagel T, Lemburg SP, Bauer TT, Nicolas V. (2003) Lipomatous Hypertrophy of the Interatrial Septum: A Prospective Study of Incidence, Imaging Findings, and Clinical Symptoms. Chest 124(6):2068-2073. (PMID: 14665481)
[3] Alpert L, Antic T. (2017) Lipomatous Hypertrophy of the Interatrial Septum. Int J Surg Pathol 25(7):611-612. (PMID: 28485184)
[4] Laura DM, Donnino R, Kim EE, Benenstein R, Freedberg RS, Saric M. (2016) Lipomatous Atrial Septal Hypertrophy: A Review of Its Anatomy, Pathophysiology, Multimodality Imaging, and Relevance to Percutaneous Interventions. J Am Soc Echocardiogr 29(8):717-723. (PMID: 27288088)
[5] Fan CM, Fischman AJ, Kwek BM, Abbara S, Aquino SL. (2005) Lipomatous hypertrophy of the interatrial septum: Increased uptake on FDG PET. Am J Roentgenol 184(1):339-342. (PMID: 15615998)
[6] Zukotynski KA, Israel DA, Kim CK (2011) FDG Uptake in lipomatous hypertrophy of the interatrial septum is not likely elated to brown adipose tissue. Clin Nucl Med 36(9):767-769. (PMID: 21825845)
URL: | https://eurorad.org/case/15835 |
DOI: | 10.1594/EURORAD/CASE.15835 |
ISSN: | 1563-4086 |
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