Medullary Thyroid Carcinoma

Abstract

Medullary thyroid carcinoma (MTC) originates from parafollicular cells (C-cells) of the thyroid gland. Calcitonin is a hormone secreted by parafollicular cells. The exact role of calcitonin is not understood, but it modulates bone mineral turnover. Medullary carcinoma accounts for less than 5 % of all thyroid cancers and is a clinically heterogeneous disease with quite variable growth rates and survival extending from months to years, sometimes decades, even when the disease is metastatic [1]. The primary treatment for this neuroendocrine tumor is surgical consisting of total thyroidectomy, with dissection of ipsilateral and central lymph nodes, which may be extended to contralateral nodes. Following surgery, patients, without lymph node involvement who have an undetectable calcitonin serum level, can be considered to be cured. For patients with persistent abnormal calcitonin serum levels, indicating residual disease or relapse, imaging generally becomes positive when calcitonin levels exceed 200 ng/L [2]. When the relapse is localized in the neck or mediastinum, single or repeated surgical resection(s) is (are) performed but are rarely followed by a normalization of calcitonin serum level. This situation is compatible, nevertheless, with long survival extending to some years and even decades without additional therapy [3]. It is important to take into consideration reliable prognostic indicators before planning systemic treatment (targeted radionuclide therapy and/or chemotherapy). Indeed, systemic treatment can be highly toxic with only a modest survival benefit. Thus, it is necessary to carefully balance the potential toxicity and benefit.