To identify risk factors for level Ⅱ and level Ⅳ lymph node metastasis in papillary thyroid carcinoma (PTC) and to evaluate the predictive value of different tumor location classification methods.

A retrospective analysis was performed on PTC patients who underwent thyroid surgery between January 2022 and May 2025. Clinical and pathological variables were collected. Tumor location was classified using the conventional longitudinal trisection method and a middle thyroid vein-based method on preoperative contrast-enhanced CT images. Univariate and multivariate logistic regression were used to analyze factors related to level Ⅱ and Ⅳ lymph node metastasis, and ROC curves were used to compare the predictive ability of different tumor location classifications.

Among 152 patients, 59 (38.82%) had level Ⅱ lymph node metastasis and 113 (73.34%) had level Ⅳ lymph node metastasis. Univariate analysis revealed that tumor location was significantly associated with metastasis in both levels (P < 0.05). Multivariate analysis showed tumor location (conventional or middle vein-based) independently predicted level Ⅱ metastasis, while middle vein-based location and level Ⅵ metastasis independently predicted level Ⅳ metastasis. ROC analysis showed that the middle vein-based classification had a higher AUC for predicting level Ⅱ metastasis than the traditional method (0.749 vs. 0.608, P < 0.05). For level Ⅳ, the AUCs were 0.687 and 0.650. This indicates better performance for predicting level Ⅱ metastasis.

Tumor location is closely associated with level Ⅱ and level Ⅳ lymph node metastasis in PTC. The middle thyroid vein-based classification may improve preoperative risk assessment of lateral cervical lymph node metastasis.