Combined categorical reporting systems of US and cytology findings for thyroid nodules: guidance on repeat fine-needle aspiration cytology.

Purpose: To investigate the usefulness of the combined categorical reporting system of ultrasonography (US) and cytology results for thyroid nodules to suggest indications of repeat US-guided fine needle aspiration cytology (FNAC). Materials and Methods: Institutional review board approval was obtained, and the requirement for informed consent was waived for this retrospective study. From June 2001 to December 2009, 1084 patients (978 women, 106 men) who underwent repeat US-guided FNAC of thyroid nodules were included. FNAC results were reported by using the Bethesda system for reporting thyroid cytopathologic findings and five thyroid US categories (category US 1, benign; US 2, probably benign; US 3, indeterminate; US 4, probably malignant; US 5, malignant). The relative risk ratios were evaluated in each separate FNAC and combined initial category by means of Cox proportional risk model. Results: Eighty-one of 1084 (7.5%) patients had malignancy over a mean follow-up time of 20.8 months (range, 3-98 months). Initial FNAC category of atypia of undetermined significance (relative risk ratio, 9.677) and US categories of US 3 (28.76), US 4 (142.0), and US 5 (411.6) had high relative risk ratios for malignancy (P < .05). Combined categories of benign cytology findings with US 3-5, non-diagnostic cytology findings with US 3-5, and atypia of undermined significance with any US categorization had high relative risk ratios of 104.80 (95% confidence interval: 53.328, 205.966). Conclusion: The combination of the categorical reporting systems between cytology and US results could be useful to suggest indications of repeat US-guided FNAC. (C) RSNA, 2012