Researchers described a very rare case of incidentally discovered medullary thyroid carcinoma (MTC) after total thyroidectomy in a patient with Graves’ disease and published their results in the American Journal of Otolaryngology.
The case was of a 70-year-old man with Graves’ disease who was referred for a total thyroidectomy. He had frequent dose fluctuations in his antithyroid medications, as well as worsening Graves’ ophthalmopathy. He elected to undergo a total thyroidectomy for definitive control of his disease. The pathology report revealed an enlarged Graves’ goiter with a single 3-mm focus of MTC confined to the thyroid that was completely excised within the total thyroidectomy specimen.
The patient was then evaluated for the possibility of aggressive disease and a germline mutation. Carcinoembryonic antigen (CEA) level was normal and calcitonin was undetectable. Genetic evaluation of germline RET mutations was also normal. A multidisciplinary tumor board discussed the case and determined to initiate active surveillance without further treatment. At the time of publication, the patient had no evidence of disease.
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“Because of the possibility of MTC in Graves’ disease patients with nodular disease, preoperative serum calcitonin can be of great value,” the authors said. “It has a higher sensitivity and specificity for detecting MTC in comparison to fine-needle aspiration cytology. It also allows for timely and disease-specific surgical management including central node dissection performed at an earlier stage.”
Since the patient did not have preoperative calcitonin levels and the low-stage MTC was an incidental discovery after the biopsy, the authors recommended measuring postoperative calcitonin and CEA levels, testing for RET mutations, and performing a neck ultrasound immediately after diagnosis. They stated that if calcitonin levels rise over time or exceed 400 pg/mL, additional imaging should be considered.
However, normally in the presence of elevated calcitonin, patients should undergo further investigation such as RET gene mutation analysis and thyroid ultrasound with fine-needle aspiration. A positive RET mutation must trigger workup for metanephrines since an occult pheochromocytoma could lead to hypertensive crisis and even death if exposed to certain medications in the perioperative period. Additionally, ruling out parathyroid adenoma is also required.
Generally, MTC originates from neural crest-derived parafollicular C-cells of the thyroid gland and occurs sporadically or in a hereditary form, accounting for only 1% to 2% of thyroid cancers in the US. This disease is rare in the Graves’ disease setting; only 15 cases in total exist in the literature, and 6 cases report incidentally discovered MTC in Graves’ disease. There is a small but significant risk of thyroid cancer in the setting of Graves’ disease, especially in patients with a palpable nodule.
Akin R, Gilley D, Tassone P. “Incidentally discovered medullary thyroid carcinoma in the post-operative Graves’ patient – a case report”. Am J Otolaryngol. Published online April 5, 2022. doi:10.1016/j.amjoto.2022.103450