Effect of the Bethesda system for reporting thyroid cytopathology on thyroidectomy rates and malignancy risk in cytologically indeterminate lesions

Abstract

Background: Cytologically indeterminate thyroid nodules represent a diagnostic and therapeutic challenge. In 2007, the National Cancer Institute recommended The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) as a means of improving the accuracy of thyroid cytopathology. Our objective was to determine the effect of TBSRTC on thyroidectomy rates and malignancy risk in cytologically indeterminate lesions.

Methods: We compared thyroidectomy rates and malignancy risk in patients with indeterminate thyroid cytopathology across 2 time periods, spanning January 2000 and November 2009; pre-TBSRTC (January 2000 to September 2003) and post-TBSRTC (June 2008 to November 2009). Statistical comparisons were performed using the Fisher's exact test and chi-square analysis (P = .05 significant).

Results: We performed 938 fine-needle aspirations in the first period, 765 in the second. We identified 78 (8.3%) cytologically indeterminate lesions in the pre-TBSRTC group and 91 (11.9%) lesions in the post-TBSRTC group. We found no difference in thyroidectomy rates between the groups (37/78 [47%] pre-Bethesda versus 32/91 [35%] post-Bethesda; P = .12). However, the malignancy rate was significantly lower in the post-TBSRTC group (13/37 [35%] pre-Bethesda versus 4/32 [13%] post-Bethesda; P = .02).

Conclusion: Application of TBSRTC is associated with lower malignancy risk in indeterminate thyroid nodules, despite similar thyroidectomy rates. These findings imply that standardization of cytologic classification improves diagnostic accuracy.