Zebra Case of Papillary Thyroid Cancer in MEN-2 Syndrome

Introduction: The occurrence of papillary thyroid cancer in patients with familial medullary thyroid cancer (FMTC) is extremely rare and underreported. Case Presentation: A 51-year-old caucasian female with no past medical history who presented to primary care physician for her annual visit. She denied any complaints. Vital signs were unremarkable. Physical examination was remarkable for large left thyroid nodule without cervical lymph nodes enlargements. Family history was significant for metastatic MTC of her two sisters (at the age of 55, 60) and her niece at age of 21. She previously declined genetic testing. Labs were unremarkable including serum calcium of 8.3 mg/dL. Thyroid function panel revealed a TSH of 2.1 μU/mL, Free T4 of 1.4 ng/dL, Thyroid peroxidase (TPO) antibody of <6 IU/mL. Neck ultrasonography revealed a mid-left thyroid hypoechoic nodule of 1.8 ×1.5 cm, without cervical lymph nodes enlargements. Fine needle biopsy revealed a papillary thyroid cancer, follicular variant. The diagnosis confirmed by two university pathologists, without any evidence of MTC. Genetic testing revealed a germline mutation in RET oncogene exons 13. Further labs revealed normal metanephrines of 12 pg/mL and normal normetanephrine of 31 pg/mL, normal serum calcitonin was less than 2 pg/mL (0-5), normal serum CEA was 2.5 ng/mL (0-5), elevated anti- thyroglobulin (anti-TG) antibodies of 1234 iu/mL (0-0.9), and elevated thyroglobulin of 50 ng/mL (1.5-38.5). The patient was referred to ENT for total thyroidectomy. Further, she was treated with radioactive iodine ablation by 155 mCi of iodine 131. Follow up whole body thyroid scan revealed no evidence of residual or recurrence. The patient was treated with 112 mcg levothyroxine with a target of TSH less than 0.1. On six months follow up, repeated neck ultrasonography revealed no remnant of thyroid tissue. Follow up Thyroglobulin (TG) was less than 0.1 ng/mL, TSH 0.05 μU/mL, FT4 of 1.98 ng/dL, and calcitonin was still less than 2 pg/ml. Genetic testing of her daughters (24, 31) revealed germline mutations in RET-oncogene exons 13 and was referred for prophylactic thyroidectomy. Discussion: FMTC is an inherited syndrome characterized by the presence of only MTC without hyperparathyroidism or pheochromocytoma and is considered a variant of MEN2A. Most cases of MEN2A have been attributed to mutations in the intracellular portion of RET, and somatic mutations in RET have been identified in 50% of cases of sporadic FMTC. We recommend in patients with germline RET mutations and a family history of MTC, the diagnosis of papillary thyroid cancer should be confirmed by two pathologists, and patients should be tested for serum calcitonin, serum calcium, and metanephrines/normetanephrine levels. Genetic testing of first-degree relatives of FMTC at an early age is essential in guiding major management decisions such as the timing of prophylactic thyroidectomy.