Thyroid Paraganglioma: A Rare Manifestation of Paraganglioma Syndrome Associated With Pathogenic Variant in SDHD.

Evaluation of an incidentally discovered indeterminate thyroid nodule (TN) in a previously healthy 59-year female led to diagnosis of thyroid paraganglioma (TPGL) and subsequently hereditary succinate dehydrogenase complex subunit D (SDHD)-related multifocal head and neck paragangliomas (PGLs). An ultrasound-guided fine needle aspiration (FNA) biopsy of the 1.7-cm TN was nondiagnostic and core biopsy was suspicious for papillary thyroid carcinoma. Pathology slides reviewed at tertiary center showed neuroendocrine neoplasm consistent with PGL. Her 24-hour urinary catecholamines and metanephrines were normal. Given the diagnosis of TPGL, genetic testing was recommended, which identified a pathogenic variant in SDHD (c.242C > T(p.P81L). Gallium-68-DOTATATE PET/CT revealed multifocal areas of increased somatostatin receptor expression from the skull base to thoracic inlet. Magnetic resonance imaging of the brain/neck showed multiple PGLs (right jugular, carotid, thyroid, left vagal, left level II, and superior mediastinal), all measured up to 1.7 cm. The right jugular PGL was treated with external beam radiation therapy of 3000 cGy. All PGLs remained stable and asymptomatic at 22-month follow-up imaging. TPGL should be considered in the differential diagnosis of a hypervascular TN in patients with SDHx-related pheochromocytoma-PGL syndromes and when such lesions with indeterminate cytology are encountered in patients with no known history of SDHx-mutation or syndrome.