RET and medullary thyroid gland carcinoma: In 26 patients, including those at risk of inherited MTC (genetic load in the family), those with aggressive MTC disease, or with the specific MEN syndrome symptoms, as well as those with the early age of onset, additional exons (5, 8, 9, 12, 18, and 19) were sequenced, to check for other mutations in the RET gene.