SAT-504 - A Mysterious Mediastinal Mass: The Role of DOTATATE-PET/CT in the Diagnosis of Nonfunctional Paragangliomas.

Introduction: Paragangliomas (PGL) are very rare, neural crest-derived neoplasms; about 2% of cases are found in the mediastinum. Mediastinal PGL is often detected incidentally, and non-functional tumors can represent a significant diagnostic challenge. We present a case of a non-functional mediastinal paraganglioma in a patient with contraindications for surgery in whom a Cu-64 DOTATATE PET/CT provided an accurate, non-invasive diagnosis, avoiding high-risk surgical biopsy.

Case Presentation: A 76-year-old male with multiple comorbidities was found to have a 2.5 x 2.2 cm hypervascular lesion in the superior mediastinum on a screening CT thorax. The patient denied symptoms suggestive of functional PGL (headaches, palpitations, or diaphoresis). Initial FDG PET/CT showed an SUV max of 4.1, which ruled out a purely vascular origin. Laboratory work up included serum chromogranin A 197 ng/ml (reference range: < 311 ng/ml ), 24-hour urine fractionated metanephrines and catecholamines; Epinephrine < 3 mcg/24 h (reference range: 2 - 24) Norepinephrine 44 mcg/24 h (reference range1: 5 – 100), Dopamine 264 mcg/24 h (reference range: 52 – 480 ), Total metanephrine 623 mcg/24 h (reference range:224 – 832), Normetanephrine 410 mcg/24 h (reference range: 122 - 676 ), Metanephrine 213 mcg/24 h ( reference range: 90 – 315 ), serum Creatinine was 1.38 (reference range: < 1.2), glomerular filtration rate (GFR) 53 (reference range >90). Cu-64 DOTATATE PET/CT revealed intense somatostatin receptor expression with a remarkably high SUV max 117.2 leading to the diagnosis of paraganglioma. Given the tumor's non-functional nature, the patient's high surgical risk, and the absence of malignant features, he was managed with clinical surveillance. Genetic testing is currently pending.

Conclusion: Non-functional mediastinal paragangliomas are rare tumors that pose a diagnostic dilemma. In challenging cases where clinical symptoms and initial biochemical tests are negative, nuclear imaging using somatostatin receptor ligands—such as DOTATATE-PET/CT—may provide, a non-invasive role in diagnosis ultimately guiding management and potentially avoiding invasive procedures specially in patients with complex medical comorbidities.

References:
1.Clinical, Genetic, Radiological Characteristics and Management of Mediastinal Paragangliomas: A Literature Review and Case Series.Quinn M, Kemkem Y, White G, et al.Endocrine-Related Cancer. 2025;32(5):e240279. doi:10.1530/ERC-24-0279.
2. European Association of Nuclear Medicine Practice Guideline/¬Society of Nuclear Medicine and Molecular Imaging Procedure Standard 2019 for Radionuclide Imaging of Phaeochromocytoma and Paraganglioma. Taïeb D, Hicks RJ, Hindié E, et al.European Journal of Nuclear Medicine and Molecular Imaging. 2019;46(10):2112-2137. doi:10.1007/s00259-019-04398-1.

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