SAT548 Incidental Papillary Thyroid Carcinoma Diagnosed After Total Thyroidectomy For Recurrent Grave's Disease

Disclosure: S.U. Perez-Martinez: None. S. Bao: None. Introduction: Whether Graves’ disease (GD) increases the risk of thyroid cancer (TC) has been a long-time topic of debate. Some studies reported increased risk of TC in GD, particularly when patients with GD have thyroid nodules. Other studies suggested the prevalence of incidental differentiated TC in GD is comparable to euthyroid goiter. Here we present a case of a 39-year-old female with a thyroid nodule and recurrent GD who underwent total thyroidectomy (TT) and was found to have a 0.4cm incidental papillary TC. Clinical case: 39 year-old female patient was diagnosed with hyperthyroidism due to GD and a 1.26x2.04x2.88cm complex right thyroid nodule at age 28, based on laboratory and thyroid ultrasound (US) studies, respectively. Fine needle aspiration showed a follicular lesion favoring colloid nodule. Patient preferred conservative measures at that time. She was treated with methimazole for 3 years and went into remission. Her thyroid nodule was monitored with serial thyroid US (every 1-2 years) for 7 years and remained stable. However, 7 years after discontinuation of methimazole, she developed recurrent hyperthyroidism, with laboratory findings of suppressed TSH of <0.04 (normal 0.35-5.5 mcu/mL), elevated free T4 of 2.4 (normal 0.8-1.8 ng/dL) and Thyroid Stimulating Immunoglobulin of 8.01 (normal < 0.054 IU/L). Patient was restarted on Methimazole 10mg daily. Her TSH remained to be low at < 0.015 (normal 0.35-3.6 mcu/mL) 4 months later, at which point more definitive treatment options including radioactive iodine ablation or TT were again discussed, and the patient opted to undergo TT, which was performed successfully 2 months later. Surgical pathology was consistent with GD, an encapsulated, fibrotic, and calcified nodule consistent with infarcted follicular lesion but also a 0.4cm incidental Papillary TC in right thyroid lobe. Surgical margin was clean, no extrathyroidal extension, one perithyroidal lymph node was negative for malignancy. Patient has been doing well afterwards. Discussion: The prevalence and clinical significance of incidental differentiated TC in patients with GD have been controversial topics. Incidence of TC in GD was mostly reported to be 7-17%, but may be as high as 42%, based on thyroidectomy studies. However, a recent retrospective multicenter study suggested the concomitant TC in GD was considerably lower. No difference in TC aggressiveness, US findings, or prognosis were observed between nodular GD and non-nodular GD groups. The clinical outcomes of TC were also excellent. A Cleveland Clinic study suggested nodule size > 1cm predicted incidental TC whereas Thyroid Stimulating Immunoglobulin titers and disease duration did not. These data argue for screening patients with GD more aggressively for TC or treating GD patients with coexisting thyroid nodule more aggressively; as in our case, even if incidental TC was found, prognosis is favorable. Presentation Date: Saturday, June 17, 2023