The first aim of this study was to explore the risk factors that were associated with central lymph node metastasis (CLNM) in patients with clinically node-negative papillary thyroid microcarcinoma (cN₀ PTMC) after prophylactic central neck dissection (PCND). The second aim was to evaluate the influence of PCND on migration of TNM staging and risk stratification (RS) in patients with cN₀ PTMC.

A total of 295 cN₀ PTMC patients who underwent thyroidectomy with PCND in the Department of General Surgery at Guangdong General Hospital between March 2014 to December 2015 were assessed retrospectively. The relations of CLNM with clinicopathologic characteristics of cN₀ PTMC were analyzed by univariate and multivariate logistic regression. The effect of PCND on migration of TNM staging and RS was also observed.

The incidence of CLNM was 42.4% (125 of 295 cases) in patients with cN₀ PTMC. Univariate analysis showed that age (P=0.000), ultrasonographic tumor size (P=0.009), pathologic tumor size (P=0.005), and multifocality (P=0.031) were significantly associated with the incidence of CLNM. No significant correlations were found between the presence of CLNM and other variables such as gender (P=0.399), bilaterality (P=0.118), capsular invasion (P=0.111), lymphovascular invasion (P=0.184), extent of thyroidectomy (P=0.319) and lymphadenectomy (P=0.458). Multivariate logistic regression analysis revealed that age <45 years (P=0.000) and multifocality (P=0.033) were independent predictors of CLNM in patients with cN₀ PTMC. Because of the identification of CLNM in the implementation of PCND, 42 (14.2%) patients were upstaged, and 118 (40.0%) patients upgraded in RS.

CLNM is highly prevalent in cN₀ PTMC. Age <45 years and multifocality are independent risk factors of CLNM in cN₀ PTMC patients. PCND can identify CLNM, which allows more accurate TNM staging/RS and may have an important impact on postoperative treatment in cN₀ PTMC patients.