Atypia of Undetermined Significance
Also written as: AUS — Atypia of Undetermined Significance
A Bethesda Category III cytological diagnosis indicating cellular abnormalities that cannot be definitively classified as benign or malignant.
Full Definition
Atypia of undetermined significance (AUS) is a diagnostic category in the Bethesda System representing thyroid FNA samples with cytological features that are neither clearly benign nor definitively suspicious for malignancy. This category encompasses cases with architectural atypia, nuclear atypia insufficient for a suspicious diagnosis, or follicular lesions with nuclear features that raise concern for papillary carcinoma. AUS carries approximately 10-30% malignancy risk and typically requires repeat FNA, molecular testing, or surgical evaluation. The category was refined in the 2017 Bethesda update to reduce diagnostic ambiguity.
Usage
Usage note: Commonly abbreviated as AUS; part of standardized Bethesda terminology.
In Context
- "The cytology showed atypia of undetermined significance, prompting repeat FNA in three months." — Pathology report
- "Molecular testing was ordered for the AUS nodule to refine risk stratification." — Endocrinology consultation