Endocrine Abstracts

Introduction: This case report described a patient who presented with medullary thyroid carcinoma (MTC) requiring a total thyroidectomy and radial neck dissection. Genetic testing performed in the context of MTC revealed RET proto-oncogene mutation. Baseline screening identified bilateral pheochromocytomas requiring treatment with bilateral adrenalectomy.

Case report: 60-year-old male patient presented with a neck lump which had been present for few years. Fine needle aspiration was in keeping with MTC, preoperative Calcitonin was 2324 ng/l. He underwent total thyroidectomy and radical neck dissection 2013. He remains under follow up and his Calcitonin fluctuates from 35-135 to date. Genetic testing revealed a heterozygous mutation in RET gene [(Heterozygous for c.1901G>A p.(Cys634Tyr)] confirming a diagnosis of MEN2 in 2019. This is no known family history of MEN related tumours in his family. His serum calcium results were consistently normal. The classical symptoms of pheochromocytoma are absent, although the clinic blood pressure was mildly elevated. Screening for pheochromocytoma with fractionated plasma metanephrines was performed in the context of known RET mutation. The first set of plasma metadrenaline was 5 times and normetadrenaline was 1.6 times the upper limit of normal. This was confirmed on repeat testing. Given the RET gene mutation and significant elevation of metadrenaline, the pre-test probability of a pheochromocytoma was very high. Subsequent MRI adrenals showed multiple nodules within both adrenal glands measuring up to 2.2 cm without any signal dropout on opposed phase imaging. Functional imaging with MIBG scan revealed avidity in bilateral adrenal nodules. Pre-operative preparation with alpha blockade to minimize the operative risks due to a sudden surge of catecholamines was undertaken. He underwent laparoscopic bilateral adrenalectomy without any complications. Histology was consistent with bilateral pheochromocytomas. Plasma metanephrines 6 weeks post-operative were normal. The patient continues surveillance follow up due to the life-long risk of recurrence of pheochromocytoma and monitoring for the MTC.

Learning points: 1. All patients with MTC should be offered genetic screening.2. MEN2 is an autosomal dominant disorder characterized by MTC (100%) with an increased risk of developing pheochromocytoma (50%) and parathyroid hyperplasia (20-30%) due to the mutations in the RET gene.3. Pheochromocytoma is rarely the initial manifestation and is often identified during screening.4. Bilateral pheochromocytomas are common in patients with MEN2.5. Genetic testing should be performed for immediate family members to allow early diagnosis followed by timely intervention to reduce the morbidity and mortality associated with MEN2.