Clinical significance of coexisting Hashimoto's thyroiditis in differentiated thyroid cancer: a retrospective cohort study.
TL;DR
Hashimoto's Thyroiditis is associated with smaller tumor size and a lower prevalence of lymph node metastasis in patients with Differentiated Thyroid Cancer, but HT is not an independent predictor of pathological tumor aggressiveness after adjustment for tumor size.
Abstract
Background
The association between Hashimoto's Thyroiditis (HT) and the clinicopathological behavior of Differentiated Thyroid Cancer (DTC) remains controversial. In particular, whether coexisting autoimmune thyroiditis independently influences invasive tumor characteristics after adjustment for tumor-related factors remains unclear. This study aimed to evaluate the relationship between HT and clinicopathological features of DTC, with a focus on tumor size, lymph node metastasis, and pathological indicators of tumor aggressiveness.
Methods
This retrospective observational study included 198 patients with histologically confirmed DTC who underwent thyroidectomy between June 2023 and March 2025. Patients were stratified according to the presence or absence of Hashimoto's Thyroiditis. Tumor size, lymph node metastasis, capsular invasion, and extrathyroidal extension were compared between groups. Tumor aggressiveness was defined as capsular invasion and/or extrathyroidal extension. Multivariate logistic regression analysis was performed to assess independent associations. Model performance was evaluated using receiver operating characteristic (ROC) analysis and nomogram visualization.
Results
Patients with coexisting HT presented with significantly smaller tumors compared with those without HT (median tumor size: 9 mm vs. 12 mm; p = 0.003). Lymph node metastasis was observed less frequently in the HT group than in the non-HT group (4.1% vs. 46.8%; p < 0.001). In multivariate analysis, tumor size was independently associated with tumor aggressiveness (odds ratio [OR] = 1.49, 95% confidence interval [CI]: 1.11-1.99; p = 0.008), whereas HT was not independently associated with aggressive pathological features (OR = 1.10, 95% CI: 0.70-1.73; p = 0.692). The predictive model demonstrated limited discriminative ability (AUC = 0.587), although calibration was acceptable.
Conclusions
Hashimoto's Thyroiditis is associated with smaller tumor size and a lower prevalence of lymph node metastasis in patients with Differentiated Thyroid Cancer. However, HT is not an independent predictor of pathological tumor aggressiveness after adjustment for tumor size. These findings suggest that HT may influence disease presentation but should not be considered a standalone prognostic factor for invasive tumor behavior. TRIAL REGISTRATION Not applicable. This study was a retrospective observational cohort study and did not involve prospective clinical trial registration.