Central Cervical Dissection for Clinical Node Negative Papillary Thyroid Carcinoma

This study is divided into three stages. In the first stage, the investigators try to explore the objective clinical imaging standard of cN0PTC on the basis of previous studies, formulate the "clinical imaging standard of cN0PTC", and randomly enroll 2000 patients under the premise of meeting the standard to establish the "predictive model of cN0‐pN+PTC". In the second stage, 2000 patients will be enrolled to test and improve the evaluation efficiency of "cN0‐pN+PTC prediction model". In the third stage, 2 000 patients without lymph node metastasis assessed by "cNo‐pN+ PTC prediction model" will be randomly divided into experimental group and control group. The experimental group will be treated with pCND, while the experimental group will be treated without pCND. The central lymph node metastasis probability, the number and size of metastatic lymph nodes in the control group will be observed after operation. The two groups will be followed up for 5, 10, 15 and 20 years to observe the RFS and OS, so as to further evaluate the "cN0‐pN+PTC prediction model" scientifically.