Should the Thyroid AUS/FLUS Category Be Further Stratified by Malignancy Risk?

摘要

The chief accomplishment of thyroid fine-needle aspiration (FNA) over the past several decades has been the reduction in the rate of unnecessary surgeries for benign thyroid nodules. With this in mind, the high negative predictive value (NPV) of a cytomorphologically benign aspirate remains the crux of this test. However, not all thyroid aspirates are clearly benign or malignant. The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) outlines 3 categories for classifying these indeterminate FNAs, each associated with a particular course of management depending on their imputed risk for malignancy: Atypia of Undetermined Significance/ Follicular Lesion of Undetermined Significance (AUS/FLUS), Suspicious for Follicular Neoplasm (SFN), and Suspicious for Malignancy. The relatively high risk of thyroid cancer in the latter 2 categories (15%-30% and 60%-75%, respectively) typically warrants surgical excision of the nodule. In contrast, in patients without other indications for thyroidectomy, the lower risk of malignancy (5%-15%) ascribed to nodules falling in the AUS/ FLUS category was felt to merit repeat FNA.