Overview of Diagnostic Terminology and Reporting

Abstract

The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) established a uniform, tiered reporting system for thyroid fine needle aspiration (FNA) specimens. TBSRTC recommends that every thyroid FNA report begin with one of six diagnostic categories: I. Nondiagnostic; II. Benign; III. Atypia of Undetermined Significance (AUS); IV. Follicular Neoplasm; V. Suspicious for Malignancy; and VI. Malignant. Each category has an implied cancer risk that averages from 4% for the “Benign” category to virtually 100% for the “Malignant” category, and, in this third edition, the malignancy risks have been revised based on additional (post 2nd edition) data. As a function of these risk associations, each category is linked to evidence-based clinical management guidelines. This chapter also includes a separate diagnostic framework for reporting pediatric thyroid FNA specimens. The recent classification of thyroid neoplasms based on molecular profiles and clinical outcomes has implications for the risk of malignancy, and this is accounted for both adult and pediatric cases in this and subsequent chapters of this book. For some of the general diagnostic categories, subcategorization can be informative and is often appropriate. Additional descriptive comments (beyond such subcategorization) are optional and left to the discretion of the cytopathologist. Notes and recommendations can be useful, especially due to the introduction of risk based classification of thyroid neoplasms, changing management strategies, and widespread use of molecular testing.