Medullary thyroid cancer (MTC), originating with parafollicular C cells, is a neuroendocrine tumor that secretes high levels of calcitonin, generally sporadic, even though 20–30% of cases are familial due to autosomal dominant germline mutations in Rearranged during Transfection (RET) proto-oncogene [4]. This evidence concerns the gene RET and medullary thyroid gland carcinoma.