Various Roles of Hashimoto's Thyroiditis and Thyroid Function in Papillary Thyroid Micro- and Macro-carcinoma

Abstract Background Thyroid cancer (TC) is one of the most prevalent endocrine cancers. Moreover, patients with Hashimoto's thyroiditis (HT) are more prone to malignant tumors. The incidence of papillary thyroid carcinoma (PTC) combined with HT is on the rise. However, a definitive consensus remains elusive. Methods We retrospectively analyzed the clinical and pathological data of 2049 patients with PTC (1033 with HT and 1016 without HT). We explored its influence on extrathyroidal extension (ETE), central lymph node metastasis (CLNM), and RAF kinase, B-type (BRAF) mutations through univariate and multivariate logistic regression analyses. Results Patients with PTC and HT exhibited a lower prevalence of ETE compared to those without HT (5.6% vs. 8.1%, P = 0.017). Notably, this trend persisted in the case of BRAF (V600E) mutations (90.1% vs. 96.2%, P < 0.001), indicating a consistent association. Multivariate logistic regression analysis revealed that HT independently predicted a reduced risk of BRAF(V600E) mutation in both PTMC (OR: 0.35, 95% CI: 0.20–0.63) and PTC (OR: 0.40, 95% CI: 0.23–0.68), even after meticulous adjustment for age and sex. Furthermore, hypothyroidism emerged as a significant risk factor for an increased prevalence of ETE in patients with PTC (OR: 2.27, 95% CI: 1.17–6.21), but not in patients with PTMC. Conclusion In conclusion, HT may reduce the occurrence of BRAF mutations in patients with PTC and PTMC, whereas patients with PTC and hypothyroidism have an elevated risk of ETE. Further research is needed to explore the underlying mechanisms and ascertain potential clinical implications.