Introduction to the Second Edition of the Bethesda System for Reporting Thyroid Cytopathology

Abstract

The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) is an evidence-based standardized reporting system for thyroid fine-needle aspiration (FNA) specimens, with six diagnostic categories that are associated with an implied risk of malignancy and clinical management scenario(s). Since its implementation in 2009, TBSRTC has been widely adopted internationally and has contributed significantly to the management of patients with thyroid nodules by increasing the quality and reproducibility of thyroid cytology reporting. As a result, considerable experience has been gained worldwide regarding its application to cytology practice, clinical impact, and limitations. In addition, several new developments have emerged in the field of thyroid pathology in recent years. These include (1) the revised ATA guidelines for the management of patients with thyroid nodules, in which risk stratification by clinical/radiological/pathological features and more conservative management are emphasized; (2) the widespread use of molecular testing of thyroid FNA samples, which has transformed the management of patients with thyroid nodules, especially in the United States; and (3) the reclassification of the encapsulated follicular variant of papillary thyroid carcinoma as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) as an attempt to reduce overdiagnosis and overtreatment of patients with this low-risk thyroid neoplasm. In light of these important advances in the management of patients with thyroid nodules and in thyroid carcinogenesis, it was an appropriate time for updating TBSRTC, and a thoroughly revised and updated second edition of the Atlas (TBSRTC 2) was published in October 2017. In this chapter, we introduce TBSRTC 2, focusing on the major changes and updates.