The contributing factors for lateral neck lymph node metastasis in papillary thyroid microcarcinoma (PTMC)

Purpose Papillary thyroid microcarcinoma (PTMC) has an excellent prognosis due to its indolent features. Only few studies have assessed the clinical factors that can predict lateral neck lymph node metastasis (LLNM) in patients with PTMC. This study aimed to examine the clinicopathological factors associated with LLNM in patients with PTMC. Methods We reviewed medical records of 3578 patients with PTMC that was <= 1 cm in diameter on final pathology at Yonsei University Hospital between January 2015 and December 2017. The patients were divided into two groups (metastasis group [n = 157] and no metastasis group [n = 3421]). Results The proportion of patients with multifocality, extrathyroidal extension (ETE), and central node metastasis was significantly higher in metastasis group (p < 0.001,p < 0.001 andp < 0.001, respectively), and the mean tumor size was relatively larger in metastasis group than in no metastasis group (0.7 +/- 0.2 vs. 0.6 +/- 0.2 cm,p < 0.001). However, no statistically significant differences were observed in the tumors harboring BRAF mutation between the two groups (84.8% vs. 80.6%,p = 0.199). Multivariate analysis indicated that the significant risk factors of LLNM include ETE (odds ratio [OR]: 1.904, 95% confidence interval [CI]: 1.267-2.861), multifocality (OR: 2.255, 95% CI: 1.544-3.293), and central node metastasis (OR: 7.768, 95% CI: 4.869-12.395), but not BRAF mutation (OR: 0.542, 95% CI: 0.337-0.874). Conclusion Approximately 4.4% of patients with PTMC presented with LLNM at the time of diagnosis. Moreover, the significant risk factors of LLNM include central node metastasis, ETE, and multifocal disease but not BRAF mutation.