Thyroid Pediatric Cancer: Role of CLND

摘要

Papillary thyroid differentiated cancer (PTC) is the most common malignancy of the thyroid gland in children. It carries an excellent overall prognosis after surgical and radioiodine (RAI) management in most cases. PTC is associated with neck metastasis in more than 60% of cases along with multifocality at the time of primary diagnosis in children. There is a higher incidence of distant metastasis in children as opposed to adults. The spread of PTC to regional lymph nodes appears to occur in a sequential pattern from the thyroid to the central compartment (Level VI and VII) and then to the ipsilateral compartment (Levels II, III and IV). Data of centers who use routine central lymph node dissection (CLND) during total thyroidectomy for PTC have found: Around 50-60% of those ‘node-negative' metastasis are in the central compartment of the neck rarely diagnosed using FNA. They can even occur in PTC with microcarcinomas (less than 10 mm tumor sizes). Cervical lymph node involvement in PTC does not affect overall survival as residual metastatic disease can be managed effectively with RAI. CLND can be performed without extension of the thyroidectomy. Routine CLND allows accurate staging of the disease. Prophylactic lateral neck dissection for patients with PTC is generally not recommended. Complications after CLND include injury to parathyroid glands, recurrent laryngeal nerve injury, superior laryngeal nerve injury and hematoma/seroma. CLND is recommended at the time of initial surgery for children with identified preoperative nodal metastasis. Since CLND decreases the risk of residual or recurrent locoregional disease and decrease the overall disease burden the efficacy of RAI treatment is increased. The most important deterrent toward prophylactic CLND in PTC in children is the high incidence found of postoperative transient vocal cord paralysis and permanent hypoparathyroidism identified. The use of neuromonitoring and higher expertise in thyroidectomy can reduce the incidence of complications. For children with clinical evidence of gross extrathyroidal invasion, locoregional metastasis on preop evaluation and/or suspicious intraoperative lymph nodes CLND is recommended to increase disease free survival. The lymph node ratio (number positive node/total nodes removed) greater than 0.45 correlates with a high risk for locoregional recurrence. Prophylactic CLND decrease overall tumor burden, guides toward lymph node ratio hence extent of disease and increase the efficacy of RAI improving survival in those children with positive nodal metastasis. Total thyroidectomy with CLND is the most efficient procedure permitting accurate staging and guiding further RAI therapy.