Objective To explored the risk factors of lymph node metastasis in papillary thyroid microcarcinoma (PTMC) by analyzing the data from the Surveillance,Epidemiology and End Results (SEER) database.
Methods The data of 31 017 patients with PTMC in the SEER database from 2002 to 2012 were retrospectively analyzed. Logistic and Cox regression analyses were used to explore the associations of the factors and the risk of lymph node metastasis in PTMC.
Results Multivariate analysis revealed that male (OR=0.673,95%CI=0.605-0.748,P=0.001),age<55 years (OR=0.683,95%CI =0.623-0.749,P=0.001),tumor size >5 mm(OR=1.172,95%CI=1.153-1.191,P=0.001),follicular variant (OR=0.641,95%CI =0.574-0.716,P=0.001),and multifocal (OR=1.662,95%CI=1.516-1.821,P=0.001) and external thyroid extension (ETE) (capsular invasion OR=1.232,95%CI=1.183-1.543,P=0.001;minor invasion OR=2.119,95%CI=1.377-3.263,P=0.001;and gross invasion OR=2.546,95%CI=2.218-2.921,P=0.001) were significantly associated with central lymph node metastasis (CLNM). Multivariate analysis revealed that tumor size >5 mm(OR=1.112,95%CI =1.091-1.133,P=0.001),male (OR=0.36,95%CI=0.322-0.401,P=0.001),age<55 years (OR=0.503,95%CI=0.453-0.559,P=0.001),follicular variant (OR=0.625,95%CI =0.549-0.711,P=0.001),multifocal (OR=2.265,95%CI =2.039-2.517,P=0.001),ETE (capsular invasion OR=2.105,95%CI=1.681-2.637,P=0.001;minor invasion OR=4.601,95%CI=3.994-5.300,P=0.001;and gross invasion OR=7.093,95%CI=4.910-10.246,P=0.001),and distant metastasis (OR=11.948,95%CI=7.523-18.975,P=0.001) were significantly associated with lateral lymph node metastasis.
Conclusions Male,young age(<55 years),large tumor(>5 mm),follicular variant-PTMC,ETE,and multifocality are the risk factors for cervical lymph node metastasis. Distant metastasis is associated with lateral lymph node metastasis. For patients at high risk of PTMC,prophylactic neck lymph node dissection is recommended.