SAT-324 Metastatic Follicular Thyroid Cancer - A Case Report

Abstract Disclosure: A. Zein Al Deen: None. A.S. Gill: None. E. Marte: None. Differentiated thyroid cancer (DTC) has seen a global rise in incidence, largely due to increased awareness and advancements in diagnostic methodologies. Despite this, DTC remains one of the few head and neck malignancies with an excellent prognosis. However, the presence of distant metastases significantly reduces survival rates, particularly in cases of metastatic follicular thyroid cancer (FTC) involving the bone. FTC is the second most common subtype of DTC, following papillary thyroid cancer. Initial treatment typically involves surgery, often supplemented with radioactive iodine (RAI) therapy. However, in metastatic cases, tumors frequently become refractory to RAI, necessitating alternative treatments such as locoregional therapies or systemic options, including kinase inhibitors. FTC metastasizes predominantly through hematogenous dissemination, with the bone and lung being the most common sites. We report the case of a 77-year-old male with a history of left follicular thyroid carcinoma. The patient initially underwent left thyroidectomy for a tumor measuring 8-9 cm, followed by a benign right thyroidectomy. Post-surgical whole-body iodine scans and biochemical evaluations were negative for disease. However, the patient subsequently developed elevated thyroglobulin levels, leading to the detection of asymptomatic metastatic disease localized to the posterior right iliac crest. Despite two rounds of RAI therapy and TSH suppression with levothyroxine, biochemical monitoring revealed persistently rising thyroglobulin levels. The most recent iodine uptake study confirmed persistent metastatic involvement of the posterior right ilium. Notably, the patient remains asymptomatic. After a detailed discussion, the patient opted against immediate external beam radiation therapy, given the absence of symptoms and the relatively aggressive nature of such intervention at this stage. Systemic treatment with kinase inhibitors was deemed premature, as these are generally reserved for symptomatic advanced disease. Active surveillance was determined to be the most appropriate course of action, along with continued TSH suppression to maintain TSH levels as low as tolerable. This case highlights the challenges in managing asymptomatic metastatic FTC and underscores the importance of individualized treatment strategies, particularly when balancing the benefits of aggressive therapies against their potential risks in asymptomatic patients. Presentation: Saturday, July 12, 2025