SAT-322 An Extremely Rare Case of Intrathyroidal Malignant Paraganglioma in an Elderly Woman

Background: Paragangliomas are uncommon tumors, usually benign, and found in younger patients. They can be sporadic or associated with a familial disorder, and can be functioning (catecholamine-secreting) or nonfunctioning. We present an extremely rare case of an elderly woman who was found to have an intrathyroidal non-functioning malignant paraganglioma. Clinical Case: A 75-year-old woman presented to the Endocrine Clinic for assessment of asymptomatic goiter found incidentally on CT scan performed for evaluation of dizziness and syncope. She denied symptoms of neck pain, dysphagia, dyspnea, and dysphonia. Medical history was significant for HTN and type 2 diabetes mellitus. Her mother had lung cancer and paternal grandmother had breast cancer; however, there was no family history of thyroid cancer or MEN. The patient has had no prior radiation exposure to her neck. Physical exam was notable for thyromegaly with multiple palpable nodules; cervical lymph node exam and Pemberton’s sign were negative. Thyroid ultrasound confirmed multiple large bilateral heterogeneous nodules. FNA of a 4.1 cm left mid nodule and a 2.5 cm right mid nodule revealed follicular lesions of unclear significance. Afirma genomic sequencing performed on the right mid nodule was suspicious for medullary thyroid cancer (MTC). TSH, calcitonin, CEA, plasma metanephrines, calcium, and iPTH were all within normal limits. CT scan of the chest/abdomen/pelvis identified a 3.6 cm mass extending from the thyroid isthmus to the retrosternal region without lymphadenopathy. Repeat FNA biopsy of bilateral thyroid nodules with calcitonin staining was negative for MTC. Total thyroidectomy with radical neck dissection was performed. Pathology revealed intrathyroidal paraganglioma with positive margins, one positive lymph node, and a focus of micropapillary thyroid carcinoma (0.8 cm). Thorough genetic testing was performed and was negative for succinate dehydrogenase (SDH) complex subunits A, AF2, B, C, and D, RET, MYC-associated factor X, NF-1, transmembrane protein 127, and VHL. Follow up PET scans remain negative for any residual mass or lymph nodes. Clinical Lessons: Paragangliomas are usually located in the neck and skull base along branches of the glossopharyngeal and vagus nerves including in and around the carotid body; intrathyroidal paragangliomas are extremely rare with just over 50 cases reported in the literature. Even rarer is the presence of metastases and the fact that our patient is elderly as almost all paragangliomas are benign and most occur in younger patients. Over 2/3 of paragangliomas are sporadic; genetic mutations of the SDH complex subtype account for most familial forms. Though most paragangliomas are asymptomatic and nonfunctioning, a functioning paraganglioma must be ruled out prior to surgery.