Comparative Evaluation of Cyclin D1 Protein Expression in Papillary Thyroid Carcinoma and Follicular Epithelial Dysplasia Associated with Hashimoto’s Thyroiditis

Abstract

Background: Hashimoto’s thyroiditis (HT) is a common autoimmune disease characterized by chronic inflammation of the thyroid gland. Cyclin D1, a key regulator of cell-cycle progression implicated in multiple malignancies, may also contribute to the pathogenesis of thyroid lesions. Objectives: This study aimed to evaluate Cyclin D1 expression in papillary thyroid carcinoma (PTC) and follicular epithelial dysplasia (FED) occurring in the context of HT. Methods: In this retrospective cohort study, patients with HT who underwent thyroidectomy at Shahid Sadoughi Hospital, Yazd, Iran, between 2014 and 2023 were evaluated. Eligibility required a histopathological diagnosis of HT accompanied by either FED or PTC. Cyclin D1 immunohistochemical expression was assessed in representative archived formalin-fixed, paraffin-embedded (FFPE) tissue blocks. Clinicopathological variables, including age, sex, and cervical lymph node involvement, were extracted from the medical records. Follow-up data were collected uniformly from all accessible patients through telephone interviews conducted at the end of the study period. For patients with PTC, follow-up included survival status and self-reported disease recurrence, whereas for patients with FED, assessment was restricted to newly developed thyroid-related clinical problems. The precise follow-up interval could not be determined because the dates of initial admission and surgery were not consistently documented in the archived files. Results: Overall, 110 patients were analyzed. The frequency of cyclin D1 expression differed significantly between the PTC and FED groups (P = 0.001). Cyclin D1 positivity was observed in all PTC cases (100%) and in 86.2% of FED cases. Cervical lymph node metastasis was documented in 28.4% of patients with PTC. At telephone follow-up, all contacted patients were alive. No patient with PTC reported recurrence, and no patient with FED reported a newly diagnosed thyroid-related clinical condition. Conclusions: Cyclin D1 expression differed between PTC and FED in patients with HT. However, because of the retrospective cohort design and the limited outcome assessment, the present study cannot determine the prognostic relevance of FED or confirm its premalignant significance. Additional longitudinal studies are required.