RET and medullary thyroid gland carcinoma: About 98% of patients with hereditary MTC havegermline mutations in exons 10, 11, 13, 14, 15, 16 and intron 16 of the REarrangementduring transfection (RET) proto-oncogene, but the etiology of the more frequent sporadicform of MTC (sMTC) is not well understood.