The Accuracy of the Cytological Examination of Fine Needle Aspiration in Papillary Thyroid Carcinoma at General Hospital H. Adam Malik (HAM), Medan Nelly Alamsyah a , Delyuzar a , T. Kemala Intan a , Nadjib Dahlan Lubis a , Betty a , Joko S. Lukito a a Department of Anatomical Pathology, Faculty of Medicine Universitas Sumatera Utara Medan, Indonesia. Abstract Background: Thyroid nodules are disorders of the thyroid gland, consisting of colloid nodules, cysts, and thyroiditis found in 80% of cases, while benign follicular neoplasms and thyroid carcinomas occur in 10%-15% and 5% of cases. The most common thyroid carcinoma is Papillary Thyroid Carcinoma (PTC), with an incidence rate of about 80% of all thyroid carcinomas. Distinguishing preoperative benign lesions is very important to prevent unnecessary surgery, therefore Fine Needle Aspiration Biopsy (FNAB) is needed, and easy to perform, this examination is the first line in evaluating preoperative thyroid lesions. Objective: Assess the accuracy of FNAB examination compared to histopathological examination in diagnosing PTC. Methods: This study is a diagnostic test. The population of this consisted of secondary data, patients with thyroid nodules diagnosed with PTC and non-PTC who underwent FNAB examination compared with Histopathological at the Anatomical Pathology Unit of General Hospital HAM, Medan. Results: Based on age group, from 62 samples, there were 56.5% PTC aged 41-60 years, (21.0%) 21-40 years, (19.4) and (3.2%) <21 years. There are 80.6% of the samples are female. PTC has a sensitivity value of 28.57%, specificity of 100%, false positive of 100%, false negative of 73.21%, and accuracy of 85.48%. Conclusion: This study can be used as a diagnostic tool for early diagnosis and a fairly accurate monitoring tool, however, a cytological diagnosis is not a substitute for a histopathological diagnosis which is still a definite diagnosis. Malignancy of PTC on cytological examination must be followed by Histopathological as the gold standard. Keywords: PTC, FNAB, sensitivity, specificity, accuracy. 1. Introduction Thyroid nodules are a common abnormality of the thyroid gland.[1-3] Palpable thyroid nodules account for about 4-7% of the population.[4] Benign thyroid tumors are a more frequent clinical finding than malignant thyroid tumors. These nodules consist of various diseases. Colloid nodules, cysts, and thyroiditis are found in about 80% of cases, while benign follicular neoplasms and thyroid carcinomas occur in about 10%-15% and 5% of cases. [2,5] Based on Globocan Burden Of Cancer (GLOBOCAN) data in 2020, the incidence of this disease is ranked 11th of all malignant diseases in the world, which is around 585,202 cases.[6] Reports based on the Surveillance, Epidemiology, and End Results (SEER) database in 2021 the incidence of thyroid cancer be 44,280 cases (2.3%) and the estimated death cases in 2021 are around 2,200 cases (0.4%), in the United States increased by an average of 3.6% per year during 1974-2013 (from 4.56 per 100,000 people/year in 1974-1977 to 14.42 per 100,000 people/year in 2010-2013), mainly related to the increase in PTC cases (annual percentage changes 4.4%).[7] Parura et al. studied thyroid cancer in the period July 2013-June 2016 at Prof. Hospital. Dr. R.D Kandou Manado. During those 3 years, the incidence of PTC increased (from 8.1% to 32.3%).[8] The most common thyroid carcinoma is PTC, with an incidence rate of about 80% of all thyroid carcinomas and the best overall prognosis.[9-13] One of the main causes of PTC, is the presence of environmental factors such as exposure to ionizing radiation, especially when it occurs in childhood. There are also many other risk factors, such as reproductive factors, genetics, dietary iodine, and others, but the factors associated with the occurrence of PTC are not fully known.[10,14,19] This carcinoma may occur at any age. Typically, this PTC occurs three times higher in women than in men, and peaks earlier in women.[15-18] The main role of FNAB lies in distinguishing between malignant and benign thyroid nodules, this greatly influences treatment decisions.[20] From 2015-2020, the sensitivity values of FNAB in the thyroid are reported to range from 50% to 98.7% and specificity from 62.5% to 98%. The accuracy of FNAB examination in detecting malignancy in thyroid lesions ranges from 62.2% to 97%.[20- 27] FNAB can categorize many benign and malignant lesions so that it can help with therapeutic protocols. This examination has been proven to be the safest and most accurate diagnostic tool for thyroid lesions.[28] When PTC was diagnosed by FNAB, 96-98.7% of cases proved to be PTC on histopathological examination.[29] 652 www.ijrp.org IJRP 2022, 110(1), 652-657; doi:.10.47119/IJRP10011011020223948