Risk Factors for and Prediction Model of Skip Metastasis to Lateral Lymph Nodes in Papillary Thyroid Carcinoma

Background Cervical lymph node metastasis is a prognostic factor of papillary thyroid carcinoma (PTC). Skip metastasis (central lymph node negative and lateral lymph node positive) of PTC is not uncommon. This study aimed to retrospectively investigate the risk factors for skip metastasis in PTC and develop a prediction model for skip metastasis. Methods A total of 745 PTC patients underwent total thyroidectomy and central plus lateral lymph node dissection at the First Affiliated Hospital of Chongqing Medical University from January 2012 to December 2017. Clinicopathological characteristics were collected and analyzed. Univariate and multivariate analyses were performed to detect the risk factors for skip metastasis. A prediction model was established based on the results of multivariate analyses. Results The skip metastasis rate was 9.7% (72/745). Age > 55 years (OR 2.63, 95% CI 1.34-5.04, p = 0.004), tumor located in the upper portion (OR 4.15, 95% CI 2.30-7.63, p = 0.001), and unilaterality (OR 2.76, 95% CI 1.14-8.23, p = 0.040) were independent risk factors for skip metastasis. Clinically lymph node-negative (cN0) patients with tumor in the upper portion (24.6%, 43/175) had higher possibility of skip metastasis than those of clinically lateral lymph node-positive (cN1b) patients (5.9%, 10/169) (p = 0.001). The area under the receiver operating characteristic curve of prediction model was 0.734 and 0.740 in derivation group and validation group, respectively. However, skip metastasis was not associated with tumor-free survival rate of PTC patients (p = 0.274). Conclusion Age > 55 years, tumor located in the upper portion, and unilaterality may increase the risk of skip metastasis. We developed the first prediction model for skip metastasis based on clinicopathological parameters in PTC patients.