Medullary thyroid carcinoma with normal serum calcitonin and carcinoembryonic levels; a case with review of literature

Introduction: Medullary thyroid carcinoma (MTC) is a primary neuroendocrine tumor originating from parafollicular C cells of the thyroid gland. The aim of the current study is to report a case of MTC with normal calcitonin level.Case report: A49-year-old male presented with a strong family history of medullary thyroid carcinoma. On ultrasound examination, the thyroid gland appeared to have a normal size but there was a welldefined solid nodule with macrocalcification, increased peri nodular vascularity and TR4. In the left thyroid lobe, mid and lower third, two adjacent nodules were seen. On blood investigations there were normal calcitonin (0.531 pg./ml) and carcinoembryonic antigen (0.984 ng/ml) levels. Total thyroidectomy was performed and the histopathological examination of the specimen revealed multifocal bilateral medullary thyroid carcinoma.Discussion: Sporadic MTC is usually unilateral, while hereditary form is bilateral. To date, only a few cases of MTC associated with normal calcitonin level have been reported. Some studies suggested that the pathophysiology of Calcitonin-negative medullary thyroid carcinoma (CTNMTC) is due to the dedifferentiation of the tumor.Conclusion: The accurate pathophysiology of medullary thyroid cancer is still unclear. More awareness regarding MTC with normal calcitonin level is required in clinical practice.(c) 2022 The Authors. Published by Elsevier Ltd on behalf of Surgical Associates Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).