Xuan V. Nguyen MD, Presenter: Nothing to Disclose

Jeff David Werner MD, Abstract Co-Author: Nothing to Disclose

Jenny K. Hoang MBBS, Abstract Co-Author: Research support, General Electric Company

To determine the prevalence of incidental thyroid nodules (ITN) on neck CT imaging and evaluate two stratification methods for management of incidental nodules.

This was a retrospective study of 848 contrast-enhanced neck CT studies over a 12-month period. After excluding 93 cases for thyroid-specific indications, known thyroid cancer or surgery, or limited visualization, 755 CT scans were evaluated for ITN ≥5 mm. Patients with nodules and >6 months of followup were evaluated with two stratification methods for malignancy risk based on A) size alone and B) size and other imaging or demographic factors. Method B emphasized different levels of risk in 3 tiered categories based on aggressive imaging features, patient age, and nodule size (Hoang et al., 2012). Medical records were reviewed to determine imaging work-up, pathology, and thyroid malignancy-free status at follow-up. Those without pathology were categorized as benign if asymptomatic at followup.  

The prevalence of ITN was 133/755 (18%). 100 patients had >6 months of follow-up and were further analyzed. Mean nodule size was 11 mm (SD 6.9). Biopsy performed in 14 patients revealed 12 benign nodules and 2 cases of thyroid lymphoma. Only 3 patients had ultrasound without biopsy. Median follow-up time in the cohort was 88 months (IQR 18-106).  Applying Method A to identify higher-risk nodules based on size alone resulted in identification of 40 patients using a ≥10-mm cutoff and 18 patients using a ≥15-mm cutoff. Both cases of malignancy were ≥15 mm. Method B with tiered risk categorization identified 24 patients: 2 in Category 1 (local invasion or suspicious adenopathy), 6 in Category 2 (age ≤35 years), and 16 in Category 3 (size ≥15 mm). Both cases of malignancy met criteria for Category 1. All nodules in Category 2 were <10 mm.   

ITN were seen in 18% of neck CTs but were rarely malignant. Increasing size cutoff from 10 mm to 15 mm halved the number of cases deemed higher-risk without missing malignancy in our cohort. Compared to using a 10 mm size cutoff, the tiered risk categorization method identifies fewer patients for work-up, but also includes imaging and demographic factors of aggressive imaging appearances and young age.  

Many radiologists use a 10 mm size cutoff to report ITN. A tiered stratification method with a 15 mm cutoff and other risk factors may be a more appropriate and cost-effective management strategy.

Nguyen, X, Werner, J, Hoang, J, Incidental Thyroid Nodules on CT: Evaluation of Risk Stratification Methods to Determine Work-up of Nodules.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12032811.html