The association of Hashimoto's thyroiditis with central lymph node metastasis in papillary thyroid cancer: a retrospective cross-sectional study.

BACKGROUND

Multiple studies have found that Hashimoto's thyroiditis (HT) is associated with the occurrence of papillary thyroid cancer (PTC). The relationship between HT and central lymph node metastasis (CLNM) in PTC remains controversial in these studies. To further explore this issue, we conducted a retrospective study and attempted to investigate it from alternative perspectives by employing a variety of statistical methods, including multivariable regression and sensitivity analyses such as propensity score matching (PSM).

METHODS

This retrospective cross-sectional study consecutively enrolled 1,123 patients (aged 16-84 years) who underwent initial thyroidectomy with central lymph node dissection at a single center [2015-2024]. HT was histologically confirmed by the presence of extensive lymphocytic infiltration with germinal center formation. CLNM was defined as histologically confirmed metastasis to at least one central lymph node (Level VI, including prelaryngeal, pretracheal, and paratracheal nodes). The primary analysis employed multivariable logistic regression on the full cohort. PSM, inverse probability of treatment weighting (IPTW) and standardized mortality ratio weighting (SMRW) were used as sensitivity analyses. Subgroup analyses were conducted to examine potential effect modification.

RESULTS

A total of 1,123 patients with PTC were involved and 243 (21.6%) patients had HT. In the primary multivariable analysis adjusting for 13 confounders, HT was independently associated with a significantly lower odds of CLNM [adjusted odds ratio (OR) =0.68; 95% confidence interval (CI): 0.49-0.94; P=0.02]. This inverse association remained robust across multiple sensitivity analyses, including PSM (OR =0.67; 95% CI: 0.47-0.96; P=0.03), IPTW (OR =0.74; 95% CI: 0.56-0.98; P=0.04), and SMRW (OR =0.70; 95% CI: 0.53-0.94; P=0.02). Subgroup analysis revealed that it was more statistically significant in female, <55 years old, multifocal tumors, without concurrent follicular adenoma.

CONCLUSIONS

This study demonstrates that HT is associated with a lower risk of CLNM in patients with PTC. Therefore, for PTC patients with HT, alternative surgical modalities such as sentinel lymph node biopsy should be explored, rather than relying solely on prophylactic central lymph node dissection.