*2.3. Surgical Treatment*

All procedures were performed by three endocrine surgeons with high experience in thyroid surgery, each performing at least 100 thyroidectomies per year. The surgical procedures were extracapsular total thyroidectomies. The RLNs were routinely exposed until their insertion into the larynx to avoid injury. Intraoperative neuromonitoring (IONM) of RLNs was routinely used in order to facilitate nerve identification and confirm its functional integrity. Parathyroid glands were searched at the usual sites and any attempt to preserve them was made.

Prophylactic CLND (pCLND) was performed in cases of clinically uninvolved lymph nodes (cN0) in tumors considered at high risk for recurrence based on family history, US features of the nodule, results of FNAC, and intraoperative examination of the thyroid gland, especially in cases of suspected extracapsular extension of the tumor. The choice to perform a pCNLD was planned and concerted among surgeons and endocrinologist preoperatively, and then discussed with the patient. CLND consisted of excision of all lymphatic structures included in level VI and level VII, on the basis of the recognized anatomic continuity between the superior mediastinum and neck. The anatomical limits of the dissection were represented anteriorly by the superficial layer of the deep cervical fascia, superiorly by the hyoid bone, laterally by the carotid arteries, inferiorly by the innominate artery, and posteriorly by the pre-vertebral layer of the deep cervical fascia. The central compartment included the pretracheal, prelaryngeal (Delphian), paratracheal, and paralaryngeal lymph nodes. Level VII was comprised of the superior anterior mediastinal lymph nodes, located above the innominate artery and below the level of the upper border of the sternal manubrium.

Patients in which only some perithyroidal lymph nodes were excised, without the clear intention to perform a pCLND, were included in the TT group.
