Researchers from Pakistan presented the very rare case of a patient with medullary thyroid carcinoma (MTC) who had normal levels of serum calcitonin and carcinoembryonic acid (CEA).

“The normal level of calcitonin and CEA does not rule out medullary carcinoma,” they wrote in a report published in Cureus, adding that “the possibility of calcitonin-negative medullary thyroid carcinoma should be considered in suitable patients.”

MTC is a rare type of neuroendocrine tumor affecting the thyroid gland that originates from parafollicular C cells. Calcitonin-negative MTC is even rarer, with almost all patients with MTC having elevated levels of calcitonin and CEA. These levels are therefore used as markers to diagnose the disease.


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The case presented here is that of a 55-year-old woman with a history of neck swelling and associated compressive symptoms lasting a few months. 

Computed tomography of her neck revealed a large nodule on her right thyroid lobe with central necrosis and retrosternal extension to the superior mediastinum. The right common carotid artery was also encased on all sides.

Fine needle aspiration and histopathological examination of the nodule showed typical features of MTC. 

The sample was analyzed immunohistochemically and tested positive for neuroendocrine markers such as synaptophysin and chromogranin A, but it was negative for calcitonin and CEA. 

The researchers also measured the levels of calcitonin and CEA in the patient’s blood, which were within the normal range. This led them to diagnose the patient with calcitonin-negative MTC. 

Due to the vascular encasement, the nodule could not be surgically removed. The team, therefore, planned external beam radiation therapy to the neck to treat the patient.

“Medullary carcinoma of the thyroid with normal serum levels of calcitonin is a very rare entity, with only a few cases reported in the literature,” they said.

Reference

Rafaey W, Munir Alvi A, Siddiqi AI, Shafiq W, Irfan H. Case report: a challenging clinical problem of calcitonin-negative medullary thyroid cancer diagnosis and surveillance. Cureus. 2022;14(11):e32088. doi:10.7759/cureus.32088