Patterns Of Central Lymph Node Metastasis Of The CN0 Papillary Thyroid Carcinoma Located In The Isthmus And Their Significance To The Choice Of Operative Method And Scope

Objective : To investigate the patterns and risk factors of central lymph node metastasis in node-negative neck(cN0)papillary thyroid carcinoma located in the isthmus.Analysis different operation methods and the postoperative complications to find out the appropriate surgical approach and scope.Methods:Forty-eight patients with cN0 papillary thyroid carcinoma located in isthmus for surgery at the First Hospital of Chongqing Medical University from January 2013 to December 2019 were reviewed retrospectively.The clinical features,including gender,age,number and size of tumer,extrathyroidal extension,and whether combined with Hashimoto’s thyroiditis,the incidence of central lymph node metastasis and related factors,the scope of surgery,postoperative complications and recurrence were analyzed.Results:Among 48 patients,27 had lymph node metastasis,with a metastatic rate of 56.25%(27/48).Lymph node metastasis in pretracheal,prelaryngeal,left and right paratracheal lymph node was present in 47.9%,22.9%,20.8% and 16.7% of the patients respectively.The proportion and risk of lymph node metastasis were significantly increased in patients with tumor size>1cm(P=0.014,OR=6.78,95%CI:1.59-28.95).In patients with the number of lymph node metastasis > 5,the incidence of tumor size >1cm,prelaryngeal,left and right paratracheal lymph node metastasis was significantly higher than that of patients with lymph node metastasis ≤5(P=0.008,P=0.033,P=0.025,P=0.027).There was a higher proportion of pretracheal or prelaryngeal lymph node metastasis in patients with left paratracheal lymph node metastasis((P=0.008,P=0.007).Multivariate analyses of risk factors associated with paratracheal lymph node metastasis indicated that the paratracheal lymph node metastasis correlated with the metastasis of pretracheal and(or)prelaryngeal lymph node(P=0.016,OR=5.92,95%CI:1.39-25.3).In 48 patients with cN0 isthmic PTC,43 cases underwent total thyroidectomy plus bilateral central lymph node dissection,and 5 patients carried out extended isthmus resection plus prelaryngeal and pretracheal lymph node dissection.21(41.8%)patients in total thyroidectomy group occurred PTH reduction,which was a transient hypoparathyroidism.48 patients were followed up for 1-6 years(37.1±9.3m)without recurrence or metastasis.Conclusion : cN0 isthmic papillary thyroid carcinoma has a high incidence of central lymph node metastasis.Pretracheal and prelaryngeal lymph node were the most common metastatic location.For patients with tumor size>1cm,a total thyroidectomy plus bilateral prophylactic central lymphadenectomy is needed.However,in patients with tumor size≤1cm and without pretracheal and prelaryngeal lymph node metastasis confirmed by intraoperative fast-frozen pathology,extended isthmus resection plus prophylactic pretracheal and prelaryngeal lymphadenectomy can be selected for reducing the complications of operation.