SAT553 A Case of Metastatic Functional Papillary Thyroid Cancer in the Setting of Graves’ Disease
Authors: Manuel Nicholas , Sternlieb Sarah Jayne , Dendy Jared , Iqbal Qasim Zafar , Olofson Andrea 
Published: October 2023

Abstract
Disclosure: N. Manuel: None. S.J. Sternlieb: None. J. Dendy: None. Q.Z. Iqbal: None.
A Case of Metastatic Functional Papillary Thyroid Cancer In the Setting of Graves’ DiseaseManuel, N., Sternlieb, S., Grissett, B., Iqbal, Q., Dendy, J. Background: Grave’s disease (GD) and papillary thyroid cancer (PTC) can be concomitant diseases. We report a rare case of metastatic PTC with concomitant GD leading to symptomatic hyperthyroidism despite total thyroidectomy. Clinical Case: A 58-year-old woman with longstanding history of thyroid nodules and left dominant nodule with benign biopsy on multiple occasions presented to her PCP with dyspnea, weight loss and globus sensation. CT of the chest was obtained revealing tracheal deviation from neck mass, mediastinal lymphadenopathy and multiple pulmonary nodules. Biopsy of lung nodule showed follicular features consistent with tumor cells of thyroid origin. She had a total thyroidectomy with central neck dissection with a final diagnosis of left sided 5 cm infiltrative follicular variant papillary thyroid carcinoma. Thyroid hormone replacement was initiated and on follow up 4 weeks later she was noted to be tachycardic at weight-based dose. At that time TSH was &lt;0.010 uIU/mL (0.400 - 4.00), free T4 was 1.96 ng/dL (0.71 – 1.51) and Thyroglobulin was found to be 31516 ng/dL (Athyrotic &lt;0.1). Prior to planned RAI she developed symptoms of dyspnea on exertion and edema and was sent to the ER for abnormal D. Dimer. Workup for PE was negative including CTA of the chest. A follow up visit showed further symptoms of hyperthyroidism with worsening fatigue, dyspnea, palpitations and new onset tremor. Levothyroxine dose was decreased further but 2 weeks later she returned to the ER with worsened thyroid function tests, and she was admitted for symptomatic hyperthyroidism. Levothyroxine was held and she was placed on PTU and propranolol. Given the overt symptomatic hyperthyroidism there were concerns for either Jod-Basedow phenomenon from iodine load with recent imaging or for hyperfunctioning PTC metastasis as the cause. Thyrotropin receptor antibody level was checked to further clarify and was elevated at 22 IU/L (0.00 – 1.75) consistent with GD. An I-131 diagnostic whole-body scan demonstrated small foci of right thyroid bed remnant and iodine-avid metastases involving mediastinal nodal disease as well as pulmonary and osseous metastases. She then underwent RAI therapy with 104.5 mCi I-131 without Thyrogen stimulation. Follow up whole body scan showed persistence of iodine-avid metastasis without any new foci of uptake compared to pretreatment scans. Conclusion: Although the coexistence of them is rare, GD should be put into the differential of rapidly progressive metastatic PTC especially if patient markedly hyperthyroid on lower doses of thyroid hormone. While functional thyroid carcinoma is rare, with less than 100 cases in literature, thorough investigation should be completed in order to not miss this concomitant disease process.
Presentation Date: Saturday, June 17, 2023