Cebrian et al. [37] carried out an association study in 135 sporadic MTC patients and 533 controls and discovered a strong association between the disease and specific haplotypes of RET. Somatic RET mutations such as M918T in MTC or pheochromocytoma of patients with a RET germline mutation appear to represent a phenomenon of tumor progression [38-43]. Here, RET is linked to medullary thyroid gland carcinoma.