SUN-LB82 Coexistence of Medullary Thyroid Cancer With Graves Disease: A Case Report

A 59 year old woman presented with enlarged thyroid, weight loss, and hot flushes. She had previously been treated for a thyroid problem in 2013 but was lost to follow up. On exam, she had a diffusely enlarged thyroid gland, without distinct nodule. She had brisk DTR’s and mild tremor. Lab results confirmed hyperthyroidism:TSH <0.01 mIU/L (0.27 to 4.2) FT4 2.4 ng/dL (0.9 to 1.8) FT3 7.95 pg/mL (1.8 to 4.6). TSI was 307 % (<140%). Thyroid ultrasound showed a few sub-centimeter nodules, and 2 clinically significant nodules on the right--1.5 x 1.2 x 1.4 cm, cystic with calcifications; and 1.3 x 0.7 x 1.2 cm hypoechoic. I-123 thyroid uptake/scan showed 61% uptake and 2 right sided cold nodules. FNA biopsy showed medullary thyroid carcinoma (MTC) with staining positive for calcitonin and negative for thyroglobulin. CT thyroid showed no adenopathy. Serum calcitonin was 71 pg/mL (<5), and CEA was elevated 5.4 ng/mL (<2.5). Work up was negative for pheochromocytoma and hyperparathyroidism.After pretreatment with methimazole, she underwent total thyroidectomy with bilateral TE groove dissection. Surgical pathology confirmed MTC pT1b pN1a. She was started on levothyroxine therapy post operatively. Discussion There are multiple reports of thyroid carcinoma (papillary and follicular) in Graves disease, but rarely MTC.(1) A recent systematic review reports only 21 total cases of MTC in patients with hyperthyroidism, of whom 15 had Graves disease.(2) MTC is derived from C-cells from the thyroid gland rather than from follicular cells. TSI, therefore, should not influence development or growth of MTC. Coexistence of the two conditions is likely coincidental rather than causative. ConclusionThyroid nodules in patients with Graves should be worked up as there is a possibility of co-existing thyroid carcinoma. This patient had hyperthyroidism with cold nodules on nuclear scan corresponding to sonographic nodules. Based on these results, she had biopsy leading to diagnosis of MTC. Follow up surgery lead to diagnosis of MTC at earlier stage and provided treatment for both conditions. References1. Staniforth, J. U. etal (2016). Thyroid carcinoma in Graves’ disease: a meta-analysis. International Journal of Surgery, 27, 118-125. 2. Sapalidis, K. etal (2019). A Rare Coexistence of Medullary Thyroid Cancer with Graves Disease: A Case Report and Systematic Review of the Literature. The American journal of case reports, 20, 1398