Thyroid incidentalomas on fluorine-18-fluorodeoxyglucose positron emission tomography-computed tomography: incidence, malignancy risk, and comparison of standardized uptake values

Can Assoc Radiol J. 2012 Nov;63(4):289-93. doi: 10.1016/j.carj.2011.04.003. Epub 2011 Dec 3.


Introduction: To determine the incidence of fluorine-18-fluorodeoxyglucose (FDG) avid thyroid incidentalomas detected on positron emission tomography (PET) with integrated computed tomography (CT), and correlate the FDG-PET-CT findings to cytology.

Methods: A total of 942 FDG-PET-CT reports were retrospectively reviewed. Patients with FDG-avid thyroid incidentalomas were further reviewed for correlative cytology.

Results: The incidence of FDG-avid thyroid incidentalomas is 2.2%. Thyroid malignancies were identified in 3 of 6 patients who underwent cytologic correlation, with a positive predictive value of 50% (95% confidence interval, 14%-86%). The mean maximum standardized uptake values of benign and malignant FDG-avid thyroid incidentalomas were 5.6 and 6.6, respectively.

Conclusion: A FDG-avid thyroid incidentaloma may predict underlying malignancy. Cytologic assessment should be considered for FDG-avid thyroid incidentalomas.

MeSH terms

  • Female
  • Fluorodeoxyglucose F18
  • Humans
  • Incidental Findings
  • Male
  • Multimodal Imaging*
  • Positron-Emission Tomography*
  • Predictive Value of Tests
  • Radiopharmaceuticals*
  • Retrospective Studies
  • Statistics, Nonparametric
  • Thyroid Neoplasms / diagnostic imaging*
  • Thyroid Neoplasms / epidemiology
  • Tomography, X-Ray Computed*


  • Radiopharmaceuticals
  • Fluorodeoxyglucose F18