Radiofrequency in Differentiated Thyroid Cancer Metastatic Lymph Node: Prospective Study of Safety and Efficacy

Inclusion Criteria: * Patients over age of 18 years * with differentiated thyroid cancer (papillary, follicular) histologically confirmed, and absence of anaplastic component * Previous treatment by total thyroidectomy and cervical lymph node dissection. * Previous treatment by at least 1 therapeutic radioactive iodine (minimum activity 740MBq) * Persistence on cervical ultrasound of at least 1 cervical metastatic lymph node, visible at ultrasound, small diameter between ≥10 mm and ≤30mm, volume maximum 20ml, spotted on a picture, and confirmed by cyto-punction * Signed informed consent Exclusion Criteria: * Location of LN metastasis with significant risk of local complication (nervous, vascular) according baseline ultrasound assessment * Patient carrier of a pacemaker or a defibrillator * Congenital or acquired hemostasis abnormality, anticoagulant therapy or double platelet antiaggregatory (aspirin and clopidogrel) * Hypersensitivity to local anesthetic * Poor general condition (performance status Eastern Cooperative Oncology Group (ECOG) \> 1) * Survival estimated less than 12 months * Patient who can't follow the instructions of RF therapy or who can't be followed during 2 years in order to meet the objectives of the study * Non affiliation to a social security * Pregnant or breast feeding women at the time of RF * Beta hormone chorionic gonadotrope (HCG) positive test (pregnancy) before RF therapy * Baseline cervical ultrasound, by expert operator trained to RF, not fulfilling feasibility criteria for RF realisation because of the location of LN metastasis or the way to reach it * Controlateral recurrent palsy on nasofibroscopy