Preoperative thyroglobulin antibody positivity is associated with delayed absorption after microwave ablation for papillary thyroid carcinoma

Background Microwave ablation (MWA) has emerged as a minimally invasive alternative to surgery for selected patients with low-risk papillary thyroid carcinoma (PTC). While thyroid autoimmunity is frequently observed in PTC, the impact of preoperative thyroid autoantibodies (TAb) on post-ablation absorption kinetics remains unclear.Methods This retrospective study included 150 patients with PTC who underwent MWA between December 2019 and December 2024 with a median follow-up of 18 months (range: 6–54 months). Patients were categorized according to preoperative thyroid autoantibody status. Volume reduction rate, complete absorption rate, tumor recurrence rate, incidence of new nodules, and thyroid function were evaluated during follow-up. Kaplan–Meier analysis and Cox proportional hazards regression were used to assess factors associated with time to complete absorption.Results During follow-up, ablation zone volume gradually decreased in all patients, but absorption was significantly slower in TAb-positive patients. The TAb-positive group exhibited a longer median time to complete absorption than the TAb-negative group (median: 30 vs. 19 months; log-rank p = 0.01). Subgroup analyses demonstrated that preoperative thyroglobulin antibody (TgAb) positivity, but not thyroid peroxidase antibody (TPOAb) positivity, was significantly associated with delayed absorption. TgAb positivity remained independently associated in multivariate Cox analysis (adjusted hazard ratio = 0.27; 95% confidence interval: 0.09–0.78; p = 0.015). No malignant recurrence occurred. TPOAb-positive patients showed a higher incidence of newly detected benign nodules. Thyroid function remained stable throughout follow-up.Conclusions Preoperative TgAb positivity is associated with delayed absorption of the ablation zone after MWA for PTC without compromising treatment completeness.