MON-333 Tall Cell Variant Papillary Thyroid Cancer in Graves’ Disease in the Absence of Discrete Thyroid Nodules

Abstract Disclosure: L. Bernacet-Rivera: None. S. Thomas: None. S. Richer: None. P. Balasubramanian: None. Background: Patients with Graves’ disease (GD) and thyroid nodules have a higher risk of cancer compared to euthyroid patients mostly accounted for by well differentiated tumors. Recent studies have shown an increased risk of aggressive variants of papillary thyroid cancer (PTC) such as tall cell variant (TCV) in patients with GD. We present a case of multifocal TCV PTC in a patient without discrete thyroid nodules on preoperative imaging. Clinical case: A 46-year-old woman with Graves’ disease diagnosed 20 years ago, managed with methimazole presented with symptoms of neck discomfort and dysphagia. Physical examination was remarkable for diffusely enlarged thyroid gland with no palpable nodules. Thyroid bruit was present on auscultation. CT neck showed enlarged heterogenous thyroid gland causing moderate tracheal compression at the thoracic inlet. She underwent total thyroidectomy due to the large goiter and compressive symptoms. Intraoperatively, a small amount of thyroid issue was left behind to preserve recurrent laryngeal nerves. Final pathology showed multifocal PTC, TCV in a background of diffuse hyperplasia and lymphocytic thyroiditis with no lymphovascular invasion or extrathyroidal extension. Of note, thyroid ultrasound (US) prior to surgery showed diffusely enlarged and hyperemic gland without discrete nodules. Post operative thyroglobulin(TG) at 6 weeks was elevated at 10 ng/mL (expected levels in an athyrotic patient are <0.1 ng/mL) with negative TG antibody. She underwent radioactive iodine remnant ablation with 31.5 mCi of I 131 and post therapy scan demonstrated thyroid origin tissue without iodine avid distant metastasis. On follow up at 1 year, TG decreased to 0.4 ng/mL and US neck showed no suspicious lymphadenopathy. Conclusion: The incidence of PTC in higher in GD patients than in euthyroid individuals. The risk is higher in patients with multiple and large nodules. Our patient lacked discrete nodules on thyroid US and was noted to have aggressive TCV cancer after surgical resection. While the mechanism of this association is not known, autoimmunity and inflammation are thought to play a role in pathogenesis of thyroid cancer in GD. Further studies are warranted to determine the pathogenesis, prevalence and prognosis although the true prevalence may be difficult to determine as most GD patients do not undergo surgery. Presentation: Monday, July 14, 2025