Medullary Thyroid Cancer

Medullary thyroid cancer (MTC) is a neuroendocrine tumor that emerges from parafollicular or C cells of the thyroid, and it consists of approximately 3–5% of malign thyroid neoplasms. The most common presentation of sporadic MTC is solitary thyroid nodule (in 75–95% of patients). Unfortunately, most patients have metastatic disease at the time of diagnosis. The serum calcitonin concentrations usually correlate with tumor volume and reflect tumor differentiation. The fine-needle aspiration (FNA) biopsy is used for the diagnosis of MTC and its sensitivity is improved by the addition of immunohistochemical staining for calcitonin. Sporadic MTC accounts for approximately 75% of all cases of the disease, and the average age of presentation is in the fourth and sixth decades of life. Inherited MTC (in 25% of patients) is transmitted in an autosomal dominant fashion and emerges as a part of the multiple endocrine neoplasia type 2 (MEN2) syndrome which is divided into two different subgroups, MEN 2A and MEN 2B. Total thyroidectomy rather than unilateral lobectomy is the preferred surgical approach because especially inherited MTC tends to be a bilateral or multifocal disease. Additional cervical lymph node dissection is made according to the findings of pre/intraoperative ultrasound identification of lymph node metastases. The initial therapy for metastatic MTC patients depends on the presence of RET mutation and could be selective and non-selective TKIs (selpercatinib, cabozantinib, or vandetanib, etc.). However, sorafenib, sunitinib, or Lenvatinib, etc. are reasonable options for patients who fail first-line treatment.