FRI368 Thyroid Paraganglioma: A Rare Manifestation Of Paraganglioma Syndrome Associated With SDHD Mutation

Disclosure: K. Samuel: None. C. McMullen: None. C. Veloski: None. S. Kushchayev: None. J.E. Hallanger-Johnson: None. J. Hernandez Prera: None. J. Muzaffar: None. G.Q. Yang: None. V. Tarasova: None. Background: Thyroid paragangliomas (TP) are exceptionally rare, representing 0.5% of all paragangliomas (PGL) with total of less than 70 cases reported to date. We report a case of a TP presenting with an indeterminate thyroid nodule, as a first manifestation of multifocal head and neck PGL, associated with succinate dehydrogenase complex subunit D (SDHD) mutation. Clinical case: A 59-year female was initially seen at the tertiary referral center for an indeterminate thyroid nodule discovered incidentally on neck ultrasound (US) ordered for evaluation of a palpable posterior left neck mass. Neck/thyroid US showed multiple nonspecific bilateral lymph nodes measuring up to 1.2 cm and a 1.7 cm right interpolar markedly hypoechoic and hypervascular solid thyroid nodule (TR5). Clinically, the patient did not have symptoms related to the thyroid nodules or lymph nodes in the neck. Thyroid function tests were within normal range. An US-guided FNA biopsy was nondiagnostic. Core biopsy was suspicious for papillary thyroid carcinoma (hypercellular thyroid parenchyma with some follicular cells with nuclear irregularity, grooves, and hyperchromasia). Pathology slides review at the tertiary center showed nondiagnostic sample (Bethesda I) on cytopathology and neuroendocrine neoplasm consistent with PGL on core biopsy (immunohistochemical stains showed tumor cells positive for synaptophysin, chromogranin and GATA3. TTF1, TG, calcitonin, CEA and AE1/3 negative). US of the neck/thyroid 4 months later showed stable disease. Calcitonin and 24-h urinary catecholamines, metanephrines were within normal limits. There was no family history of pheochromocytoma or PGL. Genetic testing showed germline SDHD mutation (p.P81L(c.242c>5). 68Ga-DOTATATE PET/CT revealed multifocal areas of increased somatostatin receptor expression from the skull base to the left thoracic inlet, which included right and left skull base lesions, left neck level IIA lymph node, right and left level III lymph nodes, right thyroid lobe lesion, and left prevascular superior mediastinal lesion. An MRI of the brain and neck with and without contrast showed 1.7 cm right jugular, 0.6 cm right carotid, and 0.6 cm left vagal PGL, 1.3 cm right thyroid nodule, left level II 1.1x.6 cm lymphadenopathy, and 0.4 cm left superior mediastinal nodule. A CT of the neck w/contrast showed multiple areas likely representing bilateral carotid body tumors, left vagal PGL, right glomus jugular, and thyroid PGL stable over 6 months. MIBG nuclear medicine scan revealed no radiotracer accumulation in the lesions. EBRT therapy is planned to the skull base lesion. Conclusions: TP should be considered in the differential diagnosis of hypervascular thyroid nodules in patients with SDH-related pheochromocytoma-PGL syndromes. This case illustrates the importance of experienced multidisciplinary team evaluation and management of complex and rare PRG cases. Presentation: Friday, June 16, 2023