American College of Radiology Thyroid Imaging Reporting System and cytopathologic classification: integration for...

The Bethesda System for Reporting Thyroid Cytopathology (BSRTC) established 6 categories with estimated risks of malignancy (ROM). The American College of Radiology developed the Thyroid Imaging and Reporting System (TIRADS) for ultrasound results. This system has 5 categories designated TIR1 to TIR5, demonstrating an increasing suspicion for malignancy. The present study investigates utility of the TIRADS designation in conjunction with each BSRTC category to see if the combination would improve the accuracy of the ROMs for each category.

Cytology records were searched for all thyroid fine needle aspirates with surgical or longer than 2-year clinical follow-up. Available TIRADS results were correlated with BSRTC categories. ROMs for the combined TIRADS and BSRTC categories were calculated based on results of surgical and clinical follow-up.

The search revealed 237 cases with adequate follow-up. BSRTC categorization was "benign" in 140, "atypia of undetermined significance" in 56, "follicular neoplasm" in 17, "suspicious for malignancy" in 10, and "malignant" in 14 cases. Cytologically benign cases designated as TIR5 had a ROM of 12%. The category of atypia of undetermined significance had 29% ROM when associated with a TIR5 designation.

Combining the BSRTC and TIRADS appears to improve identification of cases with increased ROM. Specimens designated benign (category II) but showing a TIR5 category have a ROM of 12%, compared to 2%-7% when only the BSRTC is used. The combination of TIRADS with BSRTC improves the prediction of malignancy for BSRTC category V to 90%.