An ultrasonographic tumor location-based model for predicting central lymph node metastasis in unifocal papillary thyroid microcarcinoma

Objective: Accurate preoperative assessment of central lymph node metastasis (CLNM) in patients with unifocal papillary thyroid microcarcinoma (PTMC) remains challenging. This study aimed to develop and validate a nomogram integrating tumor spatial location with clinical and ultrasonographic features for predicting central lymph node metastasis (CLNM). Methods: In this retrospective study, 432 patients with surgically confirmed unifocal PTMC were enrolled. Independent predictors were identified through univariate and multivariate regression, and a nomogram was constructed and internally validated. Results: Age ≤38 years, tumor diameter >0.95 cm, microcalcifications, suspicious central/lateral lymph nodes, tumor in the isthmus, and tumor in the middle/inferior pole adjacent to the posterior capsule were independent risk factors for CLNM, while Hashimoto's thyroiditis was protective. The nomogram showed good discrimination, with AUCs of 0.772 (training) and 0.728 (validation). Calibration and decision curve analysis confirmed clinical utility. Conclusion: The spatial location-based nomogram provides an effective preoperative tool for quantifying CLNM risk, assisting in individualized surgical planning and reducing overtreatment in unifocal PTMC.