The frequency of 'atypia of undetermined significance' interpretations for thyroid fine-needle aspirations is negatively correlated with histologically proven malignant outcomes.

OBJECTIVE

Cytopathologists' usage patterns for 'atypia of undetermined significance' (AUS) in thyroid fine-needle aspiration (FNA) are not well understood. AUS rates over a 5-year period were analyzed to quantify variability and identify correlations with experience and histologic outcomes.

STUDY DESIGN

A retrospective review of thyroid FNAs from a tertiary-care hospital from 2005 to 2009 was performed. Results were compiled for individual cytopathologists, stratified by year, and correlated with histologic outcomes.

RESULTS

Thyroid FNAs (5,327) were evaluated by 7 cytopathologists, with an overall AUS rate of 11.2%. The annual AUS rate remained relatively constant over this time period, though notable inter- and intrapathologist variability was seen. The AUS rate was significantly lower for those with cytopathology boards (10.3%) compared to those without (14.0%). There was no correlation between the AUS rate and cytopathologist experience or thyroid FNA volume. The AUS rate and malignant outcome were inversely related: the higher an individual's AUS rate was, the lower the rate of malignancy for that AUS cohort was.

CONCLUSIONS

Individual cytopathologist AUS rates were variable and often exceeded the recommended target of 7%. The application of recently published defined diagnostic criteria, along with directed cytopathologist feedback, may reduce observer variability and appropriately lower AUS utilization.