Coexistence of Type-1 Diabetes Mellitus and Papillary Thyroid Carcinoma

İntroduction: Type 1 diabetes mellitus (DM) is characterized by selective autoimmune destruction of pancreatic b-cells, resulting in insulin deficiency and associated autoimmune disorders, such as celiac disease, autoimmune thyroiditis, and gastritis, which can coexist in patients with type 1 DM. These disorders are characterized by the presence of antibodies against tissue transglutaminase, thyroglobulin, and thyroid peroxidase (TPO), as well as against gastric parietal cells. Cross-sectional studies have reported that the risk of autoimmune thyroid diseases in patients with type-1 DM is two- to threefold higher than in the general population. However, there are a few studies in the literature that investigated the relationship between malignancy and type-1 DM, and it has been shown that type-1 DM does not increase thyroid cancer. Furthermore, there is a lot of controversy regarding the role of thyroid autoimmunity in the pathogenesis of thyroid cancer. Here, a type-1 DM patient diagnosed with papillary thyroid cancer is presented. Case Report: Herein, it was aimed to present a 20-year-old female patient diagnosed with type-1 DM and subsequently with papillary thyroid carcinoma (PTC). Thyroid ultrasound revealed a 10×12×18 mm hypoechoic irregular edges nodule with macrocalcification and microcalcification foci in the left lobe and pathological lymph nodes without echogenic hilus were detected at the fourth level of the left cervical chain. Fine needle aspiration biopsy of the nodule was consistent with papillary thyroid carcinoma. Total thyroidectomy, bilateral central lymph node dissection, and left neck dissection (level II to IV) were performed. Pathological examination revealed a 1.4× 0.9 cm diameter papillary carcinoma located in the left lobe of the thyroid gland with 13 lymph node metastases. Conclusion: Patients with type 1 DM should be examined for thyroid diseases, and patients with suspected thyroid disease should be evaluated with a thyroid ultrasound. Type 1 DM and PTC can coexist, albeit very rare. It should be known that type 1 diabetes can be observed together with thyroid cancer.