Objective:To establish and validate a nomogram for predicting the probability of central lymph node metastasis (CLNM) by evaluating risk factors in clinical N 0(cN 0) stage patients with iisolated papillary thyroid carcinoma of isthmus (PTCI). Methods:Retrospectively analyzed the clinicopathological data of 112 PTCI patients who underwent surgical treatment at Lianyungang Municipal Oriental Hospital between January 2019 and December 2024. There were 35 males and 77 females, with an average age of (47.2±12.6) years, ranging from 28 to 71 years. Univariate and multivariate logistic regression analyses were performed to identify independent risk factors for CLNM. Nomogram method was used to build the transfer risk prediction model and verify it.Results:The study enrolled 112 patients, with 42 cases (37.5%) exhibiting CLNM. ROC curve analysis demonstrated that tumor diameter predicted CLNM with an AUC of 0.781 (95% CI: 0.694-0.868), identifying an optimal cutoff value of 0.9 cm (sensitivity: 0.762, specificity: 0.700). Multivariate logistic regression revealed that CLNM was independently associated with age, tumor diameter, capsular invasion, and Hashimoto′s thyroiditis (HT), all P<0.05. The logistic regression analysis results were used to construct the nomogram model of CLNM risk prediction. Hosmer lemeshow test resulted χ2=6.876, P=0.442. The calibration curves of the model group and the validation group were basically close, with an average absolute error of 0.065, P=0.099. ROC curve analysis showed that the best cut-off value of nomogram was 160 points, C-index was 0.849 (95% CI: 0.771-0.927), sensitivity was 0.786, specificity was 0.729. Decision curve analysis (DCA) based on net benefit and threshold probability shows that the nomogram can obtain net benefit in a large threshold probability range (0.13-1.00). Temporary recurrent laryngeal nerve injury occurred in 5 patients (4.5%). Temporary parathyroid injury occurred in 4 cases (3.6%), all of which were normal within one month. Conclusions:For patients with cN 0 stage isolated PTCI, CLNM is related to age ≤45 years, tumor diameter>0.9 cm, envelope invasion and HT. HT is a protective factor for CLNM. The ROC curve, calibration curve and DCA curve verified internally showed that the nomogram obtained had good discrimination ability, calibration ability and clinical applicability. When the total score ≥ 160 points indicates that the risk of CLNM is increased.