In the 42 patients with hereditary MTC, the following RET mutations were detected: C611W (n = 3), C611Y (n = 29), C618F (n = 1), C618Y (n = 3), C620R (n = 2), C634R (n = 1), C634Y + Y791F (n = 1), V804M (n = 1) and M918T (n = 1). Here, RET is linked to medullary thyroid gland carcinoma.