SAT541 Pleural Effusion As First Manifestation Of Recurrent Follicular Thyroid Cancer

Disclosure: N.S. Kadakia: None. C.A. Poku: None. Pleural effusions are a rare presentation of Follicular Thyroid Cancer (FTC). We portray a case of a patient with a remote history of FTC who presented with pleural effusion 57 years later as the first sign of recurrence. A 80 year old male presented to the hospital 8/2021 with shortness of breath and was found to have a pleural effusion. He had a history of FTC diagnosed at age 23 status post total thyroidectomy, external beam radiation and radioactive iodine. He was started on thyroid hormone replacement and was subsequently lost to follow up. Chart review showed unremarkable neck ultrasounds completed in 2004 and 2006. During admission 8/2021, a malignant pleural effusion was diagnosed after the effusion tested positive for TTF-1 and thyroglobulin (Tg). He was diagnosed with recurrent metastatic thyroid cancer. A CT scan of the neck showed a small paratracheal nodule while a PET scan revealed hypermetabolic activity in the left pleura. A neck ultrasound reported a 2 cm cervical lymph node on the right with preserved fatty hilum and an ovoid 1 cm isoechoic solid nodule in the left surgical bed. There was evidence of bulky calcified lymph nodes on CT. The pleural lesion was not accessible however biopsy of a supraclavicular lymph node was consistent with metastatic follicular carcinoma. After a delay due to iodine contrast exposure, a whole body scan with radioactive iodine was completed in 1/2022 and showed multiple foci of uptake in the right neck, right thyroid, left clavicular region, and lung bases. He was treated with 250 mCi I-131 sodium iodide in 1/2022 and levothyroxine dose was increased with a target TSH of less than 0.1. His Tg level was mildly increased. Thyroglobulin antibodies (Tg ab) were positive but have continued to trend down after treatment. A follow up CT chest done 7/2022 had persistent pleural thickening but significant improvement in pleural effusion and thus thyroxine kinase inhibitors (TKI) chemotherapy has not been initiated. Malignant pleural effusion is a rare presentation of FTC metastasis with a reported median survival of 11 months (Kazushige). Pleural effusion is a poor prognostic sign in patients with FTC and distant metastases (Broome). This affirms that prompt recognition is of essence however it also raises the question of how effective current therapies are. A retrospective study evaluated 20 patients who received RAI for pulmonary metastasis from FTC, and found the efficacy rate was relatively low (40%). There is insufficient data to determine the effectiveness of RAI as treatment for metastatic FTC to the pleura. This case adds to the limited literature on recurrence of FTC with pleural effusion and highlights limitations of current management. If the response to RAI is deemed inadequate then consideration should be given to the use of TKI. Presentation Date: Saturday, June 17, 2023