Purpose: To estimate the prevalence of incidental thyroid cancer (ITC) among patients undergoing thyroid surgery and to apply the Society of Radiologists in Ultrasound (SRU) guidelines to ITC.
Materials and methods: This HIPAA-compliant study was approved by the institutional review board, with waiver of the need to obtain informed consent. A retrospective review of data in patients who underwent thyroid surgery between January 1, 2003, and December 31, 2012, was performed. Imaging studies and reports were reviewed for ITCs that were first detected at either ultrasonography (US) or a different imaging modality and that included US as part of the work-up. ITCs were categorized by using the SRU guidelines to determine the characteristics of SRU criteria-positive and SRU criteria-negative malignancies. Patient demographic data, tumor histologic findings, tumor size, and tumor stage were compared for the SRU criteria-positive and SRU criteria-negative cancers by using the unpaired t test and the χ(2) test.
Results: Among 2090 patients who underwent thyroid surgery, 680 had thyroid cancer; of these patients, 101 (15%) had imaging-detected ITC. The SRU recommendations were applied to the findings in 90 of the 101 patients who had undergone US with images or had reports available for review. Sixteen (18%) of the 90 patients had SRU criteria-negative tumors, which represented 2% (16 of 680) of all thyroid cancers. SRU criteria-negative tumors were smaller than SRU criteria-positive tumors (mean, 1.1 cm [range, 0.9-1.4 cm] vs mean, 2.5 cm [range, 1.0-7.6 cm]; P < .001) and were more likely to be stage I (15 [94%] of 16 vs 47 [64%] of 74; P = .02).
Conclusion: Imaging-detected ITCs are uncommon. Two percent (16 of 680) of malignancies would not undergo fine-needle aspiration biopsy or surgery if the SRU guidelines were used for work-up of incidental thyroid nodules. SRU criteria-negative tumors are lower in stage than SRU criteria-positive tumors.