Risk factors and predictive model for cervical lymph node metastasis in papillary thyroid carcinoma of the isthmus: a retrospective analysis of clinical and ultrasonographic features

ObjectiveThis study aimed to investigate the clinical and ultrasonographic characteristics of papillary thyroid carcinoma (PTC) located in the thyroid isthmus and to identify independent risk factors predicting cervical lymph node metastasis (LNM).MethodsWe retrospectively analyzed 445 patients with pathology-confirmed isthmic PTC who underwent surgery at Lishui Central Hospital between December 2020 and August 2025. Based on postoperative histopathology, patients were categorized into LNM (n=160) and non-LNM (n=285) groups. Clinical and preoperative ultrasonographic features were compared between groups. Univariate and multivariate logistic regression analyzes were performed to identify independent risk factors for LNM. A predictive model was constructed and evaluated using receiver operating characteristic (ROC) curve analysis.ResultsCompared to the non-LNM group, patients in the LNM group were significantly younger (median age: 44.0 vs. 49.0 years, P = 0.012), had a higher proportion of females (70.0% vs. 62.1%, P = 0.018), and presented with larger tumors (median diameter: 9.5 vs. 6.0 mm, P < 0.001). Multivariate analysis identified maximum tumor diameter (OR = 1.15, 95% CI: 1.09–1.22, P < 0.001), female gender (OR = 1.82, 95% CI: 1.20–2.76, P = 0.004), and the presence of microcalcifications on ultrasound (OR = 1.58, 95% CI: 1.02–2.45, P = 0.040) as independent risk factors for LNM. The predictive model integrating these three factors yielded an area under the ROC curve (AUC) of 0.799 (95% CI: 0.762–0.837), with a sensitivity of 81.2% and a specificity of 66.7% at the optimal cutoff.ConclusionTumor size, female gender, and the presence of microcalcifications are independent preoperative risk factors for cervical LNM in isthmic PTC. A model based on these clinically accessible parameters provides a practical tool for preoperative risk assessment, which could help guide more individualized surgical management.