INTRODUCTION: Medullary thyroid carcinoma (CMT) is a neoplasia of parafolicular cells. The sporadic form is present in most patients, who manifest somatic mutations in the RET proto-oncogene. The remaining patients may have a germline mutation in this same gene, resulting in 3 types: familial medullary thyroid carcinoma, multiple endocrine neoplasia (MEN), subdivided into subtypes 2A and 2B. The diagnosis is ma...