Posterior minimal extrathyroidal extension as an independent risk factor for lateral lymph node metastasis in...

Extrathyroidal extension (ETE) is a risk factor for lateral lymph node metastasis (LLNM) in patients with papillary thyroid carcinoma (PTC). However, the different effects of posterior minimal extrathyroidal extension (post-mETE) and anterior minimal extrathyroidal extension (ant-mETE) on LLNM remain unclear. This research aimed to investigate the influence of post-mETE and ant-mETE on LLNM and develop a nomogram to guide perioperative management in PTC patients at high risk for LLNM.

This retrospective study included consecutive PTC patients treated from December 2017 to March 2025. The identification of clinical and pathological predictive factors for LLNM was conducted using both univariate and multivariate analytical methods, and statistically significant variables were included to construct a predictive nomogram, followed by internal validation.

Among 1798 patients with PTC, 391 cases (21.75%) were pathologically confirmed to have LLNM. Compared to ant-mETE, post-mETE was significantly associated with a higher incidence of LLNM (p<0.001). The results of the multivariate analysis showed that there were 6 independent predictive factors for LLNM: maximum tumor diameter >1 cm (OR = 3.022), bilateral thyroid involvement (OR = 2.198), multifocality of the tumor (OR = 1.374), number of central lymph node metastases ≥2 (OR = 8.083), tumor located at the upper pole (OR = 2.679), and post-mETE (OR = 2.036). The nomogram constructed in this study demonstrated good discrimination performance (AUC = 0.850) and clinical applicability.

Compared to ant-mETE, PTC patients with post-mETE were more likely to develop LLNM. The predictive nomogram demonstrated high accuracy in forecasting LLNM and facilitated the identification of occult lymph node metastases. This capability assisted in determining the need for adjuvant radioactive iodine therapy or stricter follow-up management.