Fig. 1

Receiver operating characteristic curve analysis of the number of central lymph node metastasis for predicting lateral lymph node metastasis. The results of ROC showed that the cutoff value of the number of central lymph node metastasis was 2.5, which was the optimal point to distinguish between PTC with and without lateral lymph node metastasis. At this value, the sensitivity was 53.5% and the specificity was 72.2%; AUC was 0.669, and the 95% CI was 0.599–0.739