7958 Organ Of Zuckerkandl Paragangliomas

Abstract Disclosure: L. McVicker: None. S. Egan: None. K.C. Conlon: None. J. Gibney: None. J. Feeney: None. M. Whelan: None. A. Garrahy: None. Background: The Organ of Zuckerkandl (OoZ) was first described in 1901 by an Austrian anatomist Emile Zuckerkandl as a para-aortic paraganglia located laterally to the abdominal aorta at the level of the inferior mesenteric artery. It represents the largest accumulation of extra-adrenal chromaffin cells in mammals. Paragangliomas (PGL) of the OoZ are rare entities with prior retrospective study of 371 patients with phaeochromocytoma or sympathetic PGL revealing only 21 cases of OoZ PGLs of which 14 of which (66%) had metastases at diagnosis (1). 70% of cases are in association with SDHB or less commonly, SDHD mutations (2). Clinical Case: A 48-year-old female presented with a year long history of palpitations and headache. Plasma normetanephrine level was 6340 pmol/L (lab reference 0-1180), plasma metanephrine 412 pmol/L (lab reference 0-510) and plasma 3-methoxytyramine <100 pmol/L (lab reference 0-180). CT adrenals showed normal adrenal glands. A 4.5 cm x 2.1 cm hyper-vascular retroperitoneal mass was visualised. A 68Ga-DOTATOC PET/CT showed no abnormal uptake in the area of the mass. [1]23I-MIBG scan showed increased uptake within the mass compatible with a PGL of the OoZ. Following surgery, histology confirmed PGL of the OoZ and plasma metanephrines normalised following. Genetic testing for predisposing mutation was negative. A 38-year-old male presented with sweating episodes, palpitations, and hypertension. Plasma normetanephrine level was 2,230 pmol/L (lab reference 0-1180) and plasma metanephrines 223 pmol/L (lab reference 0-520). CT adrenals showed normal adrenal glands with no other abnormalities noted. [1]23I-MIBG showed increased uptake in the region of the origin of the inferior mesenteric artery from the aorta consistent with PGL of the OoZ. The patient underwent laparoscopic resection with resultant normalisation of metanephrine levels. Histology showed a 21 mm encapsulated tumour in keeping with PGL with a PASS Score of 7. As with the first case, genetic testing for predisposing mutations returned negative. Conclusion: OoZ PGLs represent rare presentations of phaeochromocytoma-paraganglioma disease. This small case series is notable as neither case was associated with a predisposing genetic mutation, which has previously been shown to be more common in OoZ PGLs. There was also no evidence of metastasis in either case which is more commonly associated with this OoZ disease. The first case is also remarkable in terms of the tumour’s imaging characteristics. Previous studies have shown greater sensitivity using 68Ga-DOTA-Somatostatin Analogue PET/CT in comparison to [1]23I-MIBG in the detection of PGLs (3). In the first case, the tumour did not show any significant avidity on 68Ga-DOTATOC PET/CT but was avid on [1]23I-MIBG. Reference: 1. Ayala-Ramirez et al. J Clin Endocrinol Metab. 2011 2. Lodish et al. Endocr Relat Cancer. 2010 3. Carrasquillo et al. J Nuclear Medicine. 2021 Presentation: 6/2/2024