Chief Clinical Assistant Endocrine Associates of West Village New York, New York, United States
Introduction : Chromaffin cells can give rise to two types of neuroendocrine tumors. Pheochromocytomas (PCCs), which make up ~ 80% of these tumors, emerge from the adrenal medulla, while the remaining ~20% are paragangliomas (PGLs) that develop from chromaffin cells in the autonomic ganglia. Both tumors can present with symptoms of mass effect or catecholamine hypersecretion. Presented here is a case of persistently elevated catecholamines and hypertension post-surgical removal of a para-aortic PGL posing a diagnostic challenge due to initially negative imaging studies and indeterminate pathology report due to tissue contamination.
Case(s) Description : Patient SC is a 51-year-old male who presented to the clinic for a second evaluation of adrenal hyperfunction in January of 2022, five years post resection of para-aortic malignant PGL in China in October 2017. Lab results showed serum catecholamines more than four times the upper normal limit despite initially normal imaging studies in 2018, including abdominal magnetic resonance imaging (MRI), ¹⁸Flor-labeled Fluorodeoxyglucose (FDG) PET/CT, and ¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy indicating bilateral adrenal hyperactivity which may be physiologic. A subsequent abdominal MRI in April 2022 was also negative. Due to continuously elevated catecholamines, we decided to proceed with a ⁶⁸Ga-Dotatate PET/CT in May 2022, which revealed a PGL, in the inferior aspect of the right adrenal gland, five bilateral lymph node metastases, and a nodule on the left upper lung lobe. PCC could not be excluded as the margins between the mass and the adrenal gland were ill-defined. Succinate dehydrogenase genetic testing was negative. A repeat ⁶⁸Ga-Dotatate PET/CT in January 2023 demonstrated findings that confirmed PGL rather than PCC. Treatment with Lanreotide was initiated, as the avidity to Dotatate indicated sensitivity to somatostatin analogs, and the patient was referred for evaluation by an endocrine surgeon.
Discussion : In diagnosing PCC and PGL, the sensitivity and specificity of functional imaging studies depend on tumor somatostatin receptor status, catecholamine production, and glucose metabolism. FDG avidity indicates glucose transporter expression in tumors. In this case, the negative MIBG scan ruled out peptide receptor radionuclide therapy with ¹³¹I -labeled MIBG. The detection of the PGL using Dotatate bound to ⁶⁸Gallium suggested the expression of type 2 somatostatin receptors and directed the treatment with lanreotide. After initiation of Lanreotide treatment, a significant decrease in catecholamines and Chromogranin A was achieved.
