The prevalence of autoimmune thyroiditis and other autoimmune diseases in patients diagnosed with differentiated thyroid cancer association with clinical presentation and disease progression

Differentiated thyroid cancers represent the most frequently encountered malignancies of the endocrine system and encompass distinct histopathological entities including papillary thyroid carcinoma, follicular thyroid carcinoma, and Hürthle cell carcinoma. Autoimmune thyroid diseases, particularly Hashimoto's thyroiditis and Graves' disease, arise as a result of impaired immune tolerance to thyroid tissue and are characterized by chronic inflammatory responses. Current evidence suggests that sustained autoimmune-mediated inflammation may contribute to the development of thyroid malignancies. The present study aims to investigate the association between autoimmune thyroiditis and papillary thyroid carcinoma, with a specific focus on prevalence, clinicopathological features, and disease progression. Furthermore, the study explores the implications of autoimmune processes in risk stratification and therapeutic approaches to thyroid cancer. This retrospective analysis included patients diagnosed with papillary, follicular, or Hürthle cell carcinoma who were followed and treated in a tertiary care center specializing in endocrinology and metabolic diseases. A total of 474 patients were evaluated, of whom 78.5 percent were female and 21.5 percent were male. The mean age of the study population was 51.79 years with a standard deviation of 13.37. Histopathological examination revealed that 58.6 percent of cases were diagnosed with papillary carcinoma, 40.7 percent with follicular carcinoma, and 0.6 percent with Hürthle cell carcinoma. The mean tumor size was calculated as 1.39 centimeters with a standard deviation of 1.50. Statistical analysis was performed using appropriate parametric and non-parametric methods. Categorical data were analyzed using chi-square tests, while associations involving continuous variables were examined using Mann-Whitney U and Wilcoxon tests, depending on distribution characteristics. Spearman correlation analysis was applied for non-normally distributed variables. A p-value of less than 0.05 was accepted as statistically significant. The presence of lymphocytic thyroiditis was found to be significantly more common among female patients (p < 0.001). In male patients diagnosed with differentiated thyroid cancer, a higher frequency of lymphocytic thyroiditis was also observed. However, the presence of lymphocytic thyroiditis did not show a significant relationship with histopathological subtype, tumor focality, lymph node metastasis, extrathyroidal extension, or tumor localization. Notably, patients with lymphocytic thyroiditis were found to be significantly younger compared to those without (p = 0.026). While lymphocytic thyroiditis was associated with an increased risk of papillary thyroid carcinoma, it was also correlated with smaller tumor size, lower rates of metastasis, less extrathyroidal invasion, reduced recurrence rates, and a more favorable prognosis. In conclusion, chronic autoimmune inflammation may play a contributory role in the pathogenesis of differentiated thyroid malignancies. The coexistence of autoimmune thyroiditis appears to be associated not only with an increased likelihood of cancer development but also with a more indolent clinical course. These findings underscore the importance of considering autoimmune thyroid pathology in the diagnostic evaluation, therapeutic decision-making, and long-term surveillance of patients with thyroid cancer. Keywords: Differentiated Thyroid Cancer, Hashimoto's Thyroiditis, Autoimmune Diseases, Papillary Thyroid Carcinoma, Inflammation