Predictive significance of anterior and posterior minimal extrathyroidal extension for central lymph node metastasis in cN0 papillary thyroid carcinoma.

The specific role of minimal extrathyroidal extension (mETE)-particularly the differences between anterior mETE (ant-mETE) and posterior mETE (post-mETE)-in relation to Central lymph node metastasis (CLNM) for papillary thyroid carcinoma (PTC) remains uncertain. This study aimed to examine the effects of ant-mETE and post-mETE on CLNM and to construct a preoperative risk-stratification nomogram for CLNM to guide central lymph node dissection (CLND). This retrospective study analyzed 1694 consecutive clinically node-negative (cN0) PTC cases treated between 2017 and 2024. Univariate and multivariate analyses were performed to identify clinicopathological predictors of CLNM. Subsequently, a predictive nomogram incorporating significant variables was developed and internally validated. Among 1694 cN0 PTC cases analyzed, 833 (49.2%) demonstrated pathologic CLNM, and post-mETE was significantly associated with higher CLNM rates compared to ant-mETE (p < 0.001). Multivariable analysis identified seven independent CLNM predictors: age > 55 years (OR 0.466), male gender (OR 2.479), tumor size > 1 cm (OR 3.290), bilateral involvement (OR 1.335), multifocality (OR 1.420), lower pole location (OR 1.710), and mETE presence (ant-mETE OR = 2.47, post-mETE OR = 3.492). The developed nomogram demonstrated excellent discriminative ability (AUC = 0.774) and clinical utility. Both ant-mETE and post-mETE were independently associated with CLNM, with post-mETE demonstrating significantly higher metastatic propensity. The predictive nomogram developed in this study demonstrated moderate discriminative accuracy for CLNM, which could help identify occult metastases, thereby facilitating prophylactic CLND and reducing reoperation rates in patients.