MON-451 An Unusual Case of Follicular Thyroid Cancer with Pulmonary Metastasis and Concurrent Hyperthyroidism

Introduction: Follicular Thyroid Cancer (FTC) accounts for approximately 12 % of all thyroid cancers and is the second most common cause of differentiated thyroid cancer. However, coexisting hyperthyroidism and thyroid malignancy is considered a rare event and is thought to have a prevalence of 0.21–9.0 %. We describe a compelling case of metastatic FTC initially presenting with subclinical hyperthyroidism progressing to overt hyperthyroidism. Clinical Case: An 88-year-old man with a history of prostate cancer, previous tobacco dependence, and hypertension initially presented with complaints of a chronic non-productive cough associated with unintentional weight loss and fatigue. Initial imaging included a chest CT that showed several bilateral pulmonary nodules suspicious for metastatic disease, as well as an enlarged left-sided thyroid mass, which extended from the inferior pole into the mediastinum. FDG PET/CT showed avid disease identified in the lung. CT-guided lung biopsy was performed, and histopathology revealed FTC. Thyroid function tests (TFTs) revealed a Tg level of 1427 (0.00–33.70), TgAb