Lauren Waters, Tiffany Cullen, Michael Goldstein, Sheila Sheth, Chrystia M. Slywotzky, Shahidul Islam, Tamar Brandler, Gary D. Rothberger
BACKGROUND: Nondiagnostic cytology for thyroid nodules, consistent with The Bethesda System for Reporting Thyroid Cytopathology category I (B1) poses a management dilemma for clinicians. The objective of this study was to define the malignancy risk of nodules with B1 cytology using American College of Radiology Thyroid Imaging Reporting & Data System (TI-RADS) and to assess whether TI-RADS can help guide the decision to perform a repeat biopsy of these nodules. MATERIALS AND METHODS: This retrospective cohort study evaluated 139 B1 nodules that had a definitive diagnosis on repeat biopsy or surgical excision. Sonographic features were evaluated and classified according to TI-RADS. TI-RADS category and total points were compared to the final diagnosis to determine the malignancy risk of B1 thyroid nodules. RESULTS: Of the 139 nodules, 11 (7.9%) were malignant. The malignancy risk of nodules assigned TI-RADS category 1 and 2 were both 0%, TI-RADS 3 was 2.9%, whereas TI-RADS 4 and 5 were 5.9% and 46.2%, respectively. The optimal cutoff for TI-RADS points predicting malignancy was 5 points. CONCLUSION: B1 thyroid nodules in TI-RADS categories 1-3 may not require repeat biopsy given low malignancy risk. However, B1 nodules in TI-RADS categories 4 and 5 have a higher malignancy risk and thus should undergo repeat biopsy.