RET and medullary thyroid gland carcinoma: Genetic testing for RET mutations was performed in 585 people, aged 1–85 years, including 448 patients with MTC and 131 of their first- and second-degree relatives, and six patients suspected of MTC/MEN2 with other diseases (PTC, PHEO, renal carcinoma, adrenal gland tumor, nodular thyroid disease, and carcinoid of the stomach) (Table 1).