The Bethesda system of reporting FNA thyroid – its diagnostic accuracy for benign and malignant thyroid lesions

Abstract

Introduction The systems for reporting FNAC of thyroid varies in different parts of the world. In order to address terminology and other issues related to thyroid fine needle aspiration, the National Cancer Institute hosted the ’NCI Thyroid FN A State of the Science Conference’ in 2007 at Bethesda, USA. They proposed a system with 6 main diagnostic categories and their subcategories. The system is widely accepted in USA and some of the European countries where its pathological and clinical utility has been acknowledged in follow up studies. No such study however is available from our part of the world. Objective The present study was designed to determine the diagnostic accuracy of Bethesda System of reporting the fine needle aspiration cytology of thyroid. Material and methods This descriptive cross-sectional study was conducted in FN AC clinic of department of pathology, Allama Iqbal Medical College, Lahore, and Surgical units of Jinnah Hospital, Lahore, Pakistan. Data was collected from January 2012 to December 2013. A total of 130 patients with thyroid swelling were included who underwent thyroid surgery following FNAC of thyroid. FNA was reported according to Bethesda system. The histopathological examination of thyroidectomy specimen acted as the gold standard for evaluating the diagnostic accuracy of FNAC results. Results Of 130 FNACs, 7 (5.4%) cases were diagnosed as category I - non-diagnostic or unsatisfactory, 91 (70%) were diagnosed as category II - benign, 7 (5.4%) were diagnosed as category III - atypia of undetermined significance or follicular lesion of undetermined significance (AUS/FLUS), 8 (6.2%) as category IV - suspicious for follicular neoplasm, 4 (3.1%) as category V - suspicious for malignancy and 13 (10%) cases as category VI - malignant. Cytohistological correlation revealed a sensitivity of 86.4%, specificity of 85%, positive predictive value of 96.9%, negative predictive value of 53.1%, and diagnostic accuracy of 86.1% for FNAC of thyroid reported with Bethesda system. Conclusion FNAC thyroid reported by Bethesda system is a highly sensitive and specific method for differentiating benign from malignant thyroid nodules.