title: Risk stratification and prediction of cancer of focal thyroid fluorodeoxyglucose uptake during cancer evaluation.
abstract: BACKGROUND
  Focal thyroid incidentaloma by F-18 2-deoxy-2-F18-fluoro-D: -glucose (FDG) positron emission tomography (PET) has been reported 1-4% of cancer patients and normal healthy population, with a risk of cancer ranging 14-50%. The aim of this study was to investigate the prevalence of thyroid incidentaloma in F-18 FDG PET/CT and risk of cancer, usefulness of visual and SUV(max) and SUV(mean) differentiating malignant nodules and to define the predictable variables.
  
  
  METHODS
  A total 159 patients with focal thyroid FDG incidentaloma during cancer evaluation with non-thyroid cancer were enrolled. After F-18 PET/CT, we analyzed the image visually and obtained semiquantitative indices.
  
  
  RESULTS
  The incidence of focal FDG thyroid incidentaloma is 1.36% and cancer risk is 23.3%. The incidence of focal thyroid FDG uptake was significantly higher in women (2.88 vs. 0.31%; χ (2) = 136.4, p < 0.0001). Malignant thyroid incidentalomas show statistically significant higher value of SUV(max) (malignant: median 4.53, range 2.1-12.0; benign: median 3.08, range 1.6-35, p = 0.0093). However, SUV(mean) have no statistical differences (malignant: median 2.17, range 1.77-3.19; benign: median 2.05, range 1.15-5.77, p = 0.0541). In ROC analyses, the optimal visual grades were >grade 3, and the optimal semiquantitative indices were 4.46 for SUV(max), 2.03 for SUV(mean). The visual grade was superior to other variables for the differentiation malignant from benign thyroid incidentalomas. The size and visual grade was the potent predictor by logistic regression analysis.
  
  
  CONCLUSIONS
  Focal thyroid FDG incidentalomas in non-thyroid cancer patients during evaluation have a high risk of malignancy. The size and visual grade are potential predictors for malignant thyroid incidentaloma.
authors.affiliation: Department of Internal Medicine, Pusan National University Hospital, Busan, 602-739, Republic of Korea.
authors.forename: Bo Hyun
authors.initials: BH
authors.lastname: Kim
authors.forename: Min A
authors.initials: MA
authors.lastname: Na
authors.forename: In Joo
authors.initials: IJ
authors.lastname: Kim
authors.forename: Seong-Jang
authors.initials: SJ
authors.lastname: Kim
authors.forename: Yong-Ki
authors.initials: YK
authors.lastname: Kim
mesh_terms: D001692:Biological Transport; D002454:Cell Differentiation; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D033162:Incidental Findings; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D049268:Positron-Emission Tomography; D012372:ROC Curve; D012189:Retrospective Studies; D018570:Risk Assessment; D013961:Thyroid Gland / Q000000981:diagnostic imaging / Q000378:metabolism*; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000378:metabolism* / Q000473:pathology; D016606:Thyroid Nodule / Q000175:diagnosis / Q000378:metabolism / Q000473:pathology; D014057:Tomography, X-Ray Computed
chemical_list: D019788:Fluorodeoxyglucose F18