Risk Factor Analysis for Central Lymph Node Metastasis in Papillary Thyroid Microcarcinoma

Purpose: Although the prognosis of papillary thyroid microcarcinoma (PTMC) is excellent, cervical lymph node metastasis (CLNM) is commonly observed in PTMC. This study aimed to investigate the incidence and risk factors for CLNM in PTMC. Patients and Methods: Altogether, 687 patients with PTMC who initially underwent unilateral thyroidectomy with unilateral central lymph node dissection or bilateral thyroidectomy with bilateral central lymph node dissection between January 2014 and June 2018 at our hospital were included. The patients were divided into two groups: PTMC with CLNM and PTMC with no CLNM. The clinicopathologic characteristics and ultrasound features were compared between the groups. Univariate and multivariate logistic regression analyses were used to identify the risk factors for CLNM. Results: CLNM was observed in 121/687 (17.6%) patients with PTMC. PTMC patients aged <55 years exhibited a greater incidence of CLNM (87.6% vs 12.4%) than those aged >= 55 years. PTMC patients with CLNM were more likely to have capsular extension (24.0% vs 15.4%) and extension to the adjacent structures (9.9% vs 4.2%). Patients with microcalcification on ultrasound images were more likely to have CLNM (66.1% vs 47.9%). Multivariate logistic regression analysis revealed that microcalcification (odds ratio [OR]: 2.066, 95% confidence interval [CI]: 1.361-3.135, P<0.001), age <55 years (OR: 2.341, 95% CI: 1.309-4.187, P=0.004), capsular invasion (OR: 1.772, 95% CI: 1.082-2.879, P=0.023), and invasion of the adjacent tissues (OR: 2.872, 95% CI: 1.355-4.187, P=0.004) were significant risk factors for CLNM. Conclusion: Microcalcification, age <55 years, capsular invasion, and invasion of the adjacent tissues were significant risk factors for CLNM in PTMC.