Role of MIBG scintigraphy in diagnosing functional intrapericardial paragangliomas
40-year-old woman presented with labile blood pressure, dyspnea, and chest tightness. Biochemical workup for pheochromocytoma was initiated. Plasma normetanephrines, urine normetanephrines, and chromogranin A were abnormally elevated. Planar images and hybrid SPECT/CT images were obtained after administration of 123I-MIBG. These images identified a solitary focus of MIBG uptake within the thorax, specifically in the peri-atrial region of the right atrium. Correlative contrast enhanced CT of the thorax demonstrated a mass abutting the right atrium, corresponding to the collection of MIBG. Cardiac MRI depicted a T2 hyperintense mass in the right atrioventricular grove with features suggestive of tumor microinvasion. This mass also demonstrated first pass perfusion and heterogeneous late gadolinium enhancement. Functional intrapericardial paragangliomas are rare, with only close to 100 cases being reported from 1992 to 2013 [1,2]. Cardiac paragangliomas account for approximately 1% of all cardiac tumors. This case illustrates the importance of high clinical suspicion and an integrated imaging approach that takes advantage of the complimentary aspects of high resolution anatomic and functional imaging modalities to localize and characterize these elusive neoplasms. Furthermore in some instances, 123I-MIBG scintigraphy, not cross-sectional anatomic imaging, is the imaging modality which first identifies the location of these tumors--as was the case in this patient.