RET and medullary thyroid gland carcinoma: Compared with a nodal metastasis from a p.Cys634Arg MTC (control), the lymph node lesion with the p.Cys630=;Cys634Arg phenotype displayed increased expression of RET protein (Fig 4A), and the latter effect was associated with increased phosphorylation of RET’s downstream target ERK (Fig 4B).