Medullary thyroid carcinoma in children.

Medullary thyroid carcinoma (MTC) originates from thyroid parafollicular C cells, and it accounts for 5% of thyroid malignancies. MTC is sporadic in approximately 80% and hereditary in 20% of cases. When hereditary it can be associated with other benign endocrine neoplasias and/or typical nonendocrine diseases, thus configuring the multiple endocrine neoplasia syndromes (type 2, MEN2/familial MTC, FMTC). Sporadic MTC is usually diagnosed in adult life. Children with clinically evident MTC are belonging to MEN2 families, particularly MEN2A and MEN2B. Children belonging to families with FMTC are usually identified by RET genetic screening shortly after birth or during childhood but they likely develop MTC later in adult life. A genotype-phenotype correlation has been observed between RET mutations and MEN2 syndromes. As for adults, the diagnosis of childhood MTC is based on serum calcitonin (Ct) and neck ultrasound with fine-needle aspiration if a thyroid nodule is present. The standard treatment is total thyroidectomy and central neck node dissection but, according to recent evidence, if the basal Ct is <30 pg/ml or following the institutional cutoff the neck node dissection can be avoided. For advanced metastatic cases, vandetanib has been demonstrated to be effective in children as well as adults.