Fig. 4

Calibration curves of the nomogram for predicting CLNM in PTMC patients. A Calibration curve of the nomogram for training cohort. B Calibration curve of the nomogram for validation cohort. The x-axis represents the predicted CLNM. The y-axis represents the actual CLNM. The diagonal dotted line stands for a perfect prediction using an ideal model. We drew the solid line to represent the performance of the nomogram, of which the closer fit to the diagonal dotted line represents the better prediction of the nomogram. PTMC:papillary thyroid microcarcinoma;CLNM:central lymph node metastasis