Tumor size is the strongest predictor of microscopic lymph node metastasis and lymph node recurrence of N0 papillary thyroid carcinoma.

It is well-known that papillary thyroid carcinoma (PTC) frequently metastasizes to the regional (central and lateral) lymph nodes, even though it is diagnosed as node-negative on preoperative imaging studies. In this study, we investigated predictors of microscopic node metastasis and lymph node recurrence of PTC without node metastasis detected preoperatively (N0). Of the clinicopathological features that can be evaluated pre- and intraoperatively, tumor size (> 2 cm) was the strongest predictor of microscopic central and lateral node metastasis on multivariate logistic analysis. Also, the tumor size most markedly affected lymph node recurrence, but not distant recurrence. Lymph node recurrence may not be immediately life-threatening, but it can be a stressor both for physicians and patients. Therefore, careful lymph node dissection is recommended for PTC with a large size, even though it is prophylactic.