Germline RET mutation analysis currently plays a pivotal role in the clinical management of MTC, which should be offered to the following individuals (2, 51): (1) all MEN2 patients; (2) first-degree relatives of hereditary MTC patients; (3) CLA patients; (4) HD patients; (5) parents whose infants or young children have the classic phenotype of MEN2B; and (6) “sporadic MTC” patients (2). This evidence concerns the gene RET and medullary thyroid gland carcinoma.