The relationship between central lymph node metastasis and the distance from tumor to thyroid capsule in papillary thyroid microcarcinoma without capsule invasion.

backgroundThis study aims to explore the predictive factors of central lymph node metastasis (CLNM) in patients with papillary thyroid microcarcinoma (PTMC) without capsule invasion.

methodsFrom January 2016 to October 2018, 1,622 patients with PTMC, who underwent surgical treatment at Zhejiang Cancer Hospital, were enrolled in the present study. A model of multivariate logistic regression was developed to find the variables that were independently associated with CLNM. The results were presented in the odds ratio (OR) with a 95% confidence interval (CI). The nomogram for predicting CLNM was developed based on the results of the multivariate logistic regression analysis. The distance (distance >0) from tumor to capsule is defined as the shortest distance from the tumor boundary to the capsule or trachea.

resultsThe multivariate logistic regression analysis indicated that age, gender, tumor maximum diameter, tumor mean diameter, and tumor volume were independently associated with CLNM. In the 692 cases without capsular invasion, the distance from the capsule was not correlated to the CLNM. The joint model, which included age, gender, tumor volume, and capsular invasion, were analyzed using the ROC curve. The cut-off point for the prediction of CLNM was defined as a value of 0.208. The area under the ROC curve was 0.687, the sensitivity was 65.4%, and the specificity was 63.3%.

conclusionsGender, age, maximum diameter, mean diameter, tumor volume, and capsular invasion were independently associated with the CLNM. When there was no capsular invasion, the distance between the tumor and capsule was not correlated to the CLNM, suggesting that considering whether the tumor is close to the capsule may not be necessary for low-risk PTMC.