Relationship between hashimoto thyroiditis and thyroid nodule cytology and thyroid cancer

Introduction and Aim: The impact of Hashimoto thyroiditis (HT) on the risk of papillary thyroid cancer (PTC) still remains unclear. The aim of this study is to determine the clinical, sonographic and cytological findings in patients with thyroid nodules with HT; to determine whether there is a difference between the findings in patients with thyroid nodules without the diagnosis of HT and to evaluate whether Hashimoto thyroiditis has an impact on the malignancy risk category of thyroid nodules. Material and method: A total of 1200 patients who underwent nodule evaluation between 2017-2019 in the Endocrinology and Metabolism clinic of Gaziantep University Faculty of Medicine were included in the study. The diagnosis of HT was made based on elevated thyroid peroxidase antibody (TPOAb) level and findings of diffuse heterogeneity on ultrasound, and/or the finding of diffuse lymphocytic thyroiditis on histopathology. The patients were evaluated in 2 groups as HT and non-HT. The demographic characteristics of patients, sonographic features of the thyroid gland and the cytology of thyroid nodules were compared in both groups. The patients who were diagnosed thyroid cancer after thyroidectomy (papillary thyroid carcinoma, follicular carcinoma, medullary carcinoma, anaplastic carcinoma, primary thyroid lymphoma, and others)in HT and non-HT groups were determined. The prognostic parameters associated with malignancy risk were compared in both of groups. The impact of HT on the distribution of nodule cytology and, ultimately, on malignancy risk was investigated. Results: A total of 252 patients (21.1%) were diagnosed for HT with thyroid nodules (HT group)and 943 patients (78.9%) were diagnosed for non-HT with thyroid nodules (non-HT group). The mean age of the patients was 47 ± 13 years in the non-HT group, and was 46 ± 13 years in the HT group. In non-HT group, 84.9% were women and 15.1% were men. In HT group, 89.3% were women and 10.7% were men. The prevalence of indeterminate cytology was higher in theHT group compared with the non- HT group(18.60% vs 10.80%, P=0.001). The frequency of PTC was statistically significantly higher in HT group than non-HT group (%22.2 vs %5.7, p=0.001). However, there was not an association between the histopathologic subtypes of PTC and HT. Although the average TSH levels were higher in the HT group than non-HT group, we did not find a relationship between high TSH levels and frequency of PTC in both groups (respectively, p=0.341 and p=0.944). Conclusion: In our study, it was found that papillary thyroid carcinoma was observed more frequently in patients with Hashimoto thyroiditis. According to the Bethesda classification, the frequency of category 5 (suspicion of malignancy) was significantly higher in the HT group than in the non-HT group. According to our findings, diffuse sonographic heterogeneity and/or TPOAb positivity should be taken in consideration at the time of assesment of malignancy in thyroid nodules. As a result, it would be a rationalistic approach to evaluate carefully for cytological examination of thyroid nodules particularly with HT. Keywords: Hashimoto thyroiditis, papillary thyroid cancer, thyroid nodule