SUN-621 Lessons from beyond the Graves'

Abstract

Introduction: The coexistence of thyrotoxicosis and thyroid carcinoma is a well-recognised clinical phenomenon. Patients with Graves’ disease have an increased risk of developing thyroid carcinomas than in patients with toxic adenoma or toxic multinodular goiter. We report a patient with Graves’ disease who had a ‘silent’ thyroid cancer. Clinical Case: A 20 year-old female was diagnosed with Graves’ disease. She had clinical signs of Graves’ ophthalmopathy, a thyroid goiter, sinus tachycardia and unintentional weight loss. Her TSH level was <0.005 mIU/L [0.40 - 3.50 mIU/L], free T4 level was 40.9 pmol/L [9.0 - 19.0 pmol/L], free T3 level was >46.1 pmol/L [2.6 - 6.0 pmol/L] and TSH receptor antibody (TRAb) level was 27.5 IU/L [<1.0 IU/L]. She denied prior head/neck irradiation or a family history of thyroid disorders. She was commenced on carbimazole.   Her initial thyroid ultrasound (January 2016) demonstrated a heterogenous, hypervascular goiter (right lobe measured 65 x 31 x 25 mm and left lobe measured 50 x 21 x 31 mm). On her repeat thyroid ultrasound (April 2017), the heterogeneous hypervascular goiter had increased in size (right lobe 81 x 37 x 36 mm and left lobe 64 x 31 x 36 mm). A thyroid technetium scan identified diffuse radiotracer uptake (82.51%), consistent with Graves’ disease. Due to refractory Graves’ disease and the presence of Graves’ ophthalmopathy, a total thyroidectomy was performed (February 2018). Surprisingly, post-operative histopathology identified a 60 mm papillary thyroid carcinoma in the right lobe and a 36 mm papillary thyroid carcinoma in the left lobe, with lymphovascular and adipose tissue invasion. The tumours were negative for BRAF V600E. The remaining thyroid tissue showed Graves’ thyroiditis. Six weeks post-thyroidectomy, she had a thyroglobulin level at 16.3 μg/L [0 - 28 μg/L], undetectable anti-thyroglobulin antibody and TRAb level at 4.4 IU/L. Radioactive iodine remnant ablation was performed (August 2018) with steroid cover for persisting Graves’ ophthalmopathy. Her whole body I-131 scan identified residual thyroidal type tissue in the thyroid bed and diffuse uptake throughout both lungs, likely secondary to inflammation from a flu-like illness prior to her scan. Her thyroglobulin levels had reduced to 1.1 μg/L, with TSH level of 12 mIU/L, free T4 level of 18 pmol/L and free T3 level of 3.3 pmol/L. Conclusions: Patients with Graves’ disease have an increased risk of thyroid carcinomas, possibly related to TSH receptor antibodies. It is usually either clinically apparent or occult micro-carcinomas. Large papillary thyroid carcinomas in Graves’ disease not detected by thyroid technetium scan or thyroid ultrasound is rare.