Predictive Factors of Lateral Lymph Node Metastasis in Papillary Thyroid Microcarcinoma

This study was designed to determine the incidence and predictive factors for lateral lymph node metastasis (LNM) in patients with papillary thyroid microcarcinoma (PTMC). From January 2014 to July 2015, a retrospective review was conducted of 215 patients with PTMC who underwent total thyroidectomy and central lymph node dissection (LND) with lateral LND. Correlations of lateral LNM with clinicopathological features were examined using univariate analyses. Risk factors for lateral LNM were identified by multivariate analysis. Lateral LNM was observed in 163(75.8%) cases of 215 patients and often involved in level III (82.2%) and level IV (65.6%), with most found in two-levels (41.1%) and single-level (33.7%) models. Multivariate analyses showed that central LNM (odds ratio [OR]: 8.28, 95% confidence interval [CI]: 3.43-19.98, p < 0.001) and upper portion location (OR: 2.87 [CI: 1.34-6.09]; p = 0.007) were independent predictive factors for lateral LNM. The incidence of skip metastasis-Lateral LNM with central Lymph nodes negative-was 8.6% (14/163). Age ≥ 45 years old (OR: 4.37 [CI: 1.14-16.66]; p = 0.031) and upper portion location (OR: 4.34 [CI: 1.27-14.78]; p = 0.019) were independent risk factors for skip metastasis by multivariate analyses. Taken together, patients with PTMC with central LNM and tumor in the upper pole were more likely to present with lateral LNM. Even if there was no central LNM, patients with an age ≥ 45 years old and tumors in the upper portion of the thyroid should be evaluated carefully for possible lateral LNM.