Lymph node density in papillary thyroid carcinoma is a prognostic factor after adjusting for pathological stage

We investigated the possible association between the lymph node density and survival outcomes in differentiated papillary thyroid carcinoma, and examined whether the lymph node density was a predictor in a multivariate analysis adjusted for the pathological stage in the eighth edition of the Union for International Cancer Control Tumor-Node Metastasis Classification of Malignant Tumors. A total of 543 patients with papillary thyroid carcinoma were enrolled. We performed restaging according to the eighth edition. The lymph node density was the ratio between number of positive lymph nodes and total number of excised lymph nodes. A log-rank test and Cox's proportional hazards model were used for univariate and multivariate analysis with adjustment for the pathological stage in the eighth edition, respectively. In both the univariate and multivariate analyses of 150 patients with pN1bM0, the presence of a lymph node density of ≥ 0.3 with pN1b was significantly associated with shorter disease-specific survival. In both the univariate and multivariate analyses of all 543 patients, a lymph node density of ≥ 0.3 with pN1b were also significantly associated with shorter overall and disease-specific survival. In conclusion, these results suggest that the lymph node density can be used as a predictor for the survival outcomes after adjustment for the pathological stage in the eighth edition.