P409 - ECE_2414 - Association of hashimoto thyroiditis with tumor characteristics and recurrence in papillary thyroid carcinoma

Abstract

The relationship between Hashimoto thyroiditis (HT) and papillary thyroid carcinoma (PTC) remains controversial. This study aimed to evaluate the clinicopathologic characteristics and prognostic impact of coexisting HT in patients with PTC. A total of 6581 patients who underwent surgery for PTC were retrospectively analyzed. Patients were classified into control (n = 5396) and HT (n = 1185) groups based on histopathologic diagnosis. Clinicopathologic features, molecular profiles, surgical extent, and recurrence-free survival (RFS) were compared. Multivariate logistic regression analysis was performed to identify factors associated with coexisting HT. RFS was analyzed using the Kaplan–Meier method. Patients with HT were more likely to be female and younger (both P < .001). Total thyroidectomy and central lymph node dissection were more frequently performed in the HT group (P = .005 and P = .003, respectively). HT was associated with higher rates of multifocality (P < .001) but showed no significant differences in tumor size, vascular invasion, lymphatic invasion, extrathyroidal extension, or lateral lymph node metastasis. The HT group demonstrated a lower prevalence of BRAF mutation (72.2% vs 84.7%, P < .001), while TERT mutation rates were comparable. Preoperative TSH, thyroglobulin, and anti-thyroglobulin antibody levels were significantly higher in patients with HT (all P < .001). On multivariate analysis, female sex, younger age, multifocal disease, absence of extrathyroidal extension, absence of BRAF mutation, and higher preoperative anti-thyroglobulin antibody levels were independently associated with coexisting HT. During follow-up, recurrence rates did not differ significantly between groups (3.2% vs 3.4%, P = .726), and Kaplan–Meier analysis showed no significant difference in RFS (P = .73). Coexisting Hashimoto thyroiditis in PTC is associated with distinct clinicopathologic and molecular characteristics, including female predominance, multifocality, and lower BRAF mutation rates. However, HT does not appear to influence recurrence-free survival. These findings suggest that while HT affects tumor presentation, it has limited prognostic impact on long-term outcomes in PTC.