To investigate the risk factors for high-volume (>5) lymph node metastasis (HVLNM) in papillary thyroid carcinoma with Hashimoto's thyroiditis.

One hundred and sixty-nine consecutive PTC patients with HT who underwent total thyroidectomy with central and lateral lymph node dissection from January 2018 to June 2023 at the Kunshan First People's Hospital were included in the study. Univariate and multivariate logistic regression analyses were conducted to identify the risk factors for HVLNM in PTC patients with HT.

Tumor size, extrathyroidal extension (ETE), and presence of vascularity were identified to be independent risk factors for HVLNM in PTC patients with HT. A predictive model for HVLNM was then developed based on these independent risk factors. The area under the curve (AUC) of the model for predicting HVLNM was 0.932. The risk score of HVLNM was calculated as 1.510 × (if tumor size ≥ 10 mm) + 3.267 × (if ETE is present) + 1.580 × (if vascularity is present).

Tumor size, ETE, and the presence of vascularity are risk factors for the occurrence of HVLNM in PTC patients with HT. The prediction model constructed based on these risk factors has good efficacy in predicting the development of HVLNM in PTC patients with HT, which is expected to provide useful information for clinicians to formulate personalized treatment plans for such patients.