Lymph node metastasis of papillary thyroid carcinoma in the context of Hashimoto's thyroiditis

Background Whether Hashimoto's thyroiditis (HT) affects the lymph node metastasis of papillary thyroid carcinoma (PTC) remains uncertain. The diagnostic criteria for HT differed in previous studies. Our study focused on analysing the influence of HT on PTC lymph node metastasis (LNM) with stringent diagnostic criteria for HT. Methods A total of 444 patients diagnosed with PTC from 2019 to 2020 were enrolled and divided into two groups: HT group and non-HT group. Diagnostic criteria of HT were as follows: thyroid peroxidase antibody (+) and postoperative histopathology of Hashimoto's disease. Results There was no significant difference in the LNM rate between HT group and non-HT group. Patients in the HT group had fewer numbers of metastatic LNs and lower metastatic LNs ratio in central region. In the HT group, age < 55 and tumor size >= 10 mm were independent risk factors for central LNM. Conclusion The autoimmune response of HT seems to reduce the central lymph node metastasis of HT PTCs. Age < 55 and tumor size >= 10 mm were independent risk factors of central lymph node metastasis in HT PTCs.