title: The clinical significance and management of incidental focal FDG uptake in the thyroid gland on positron emission tomography/computed tomography (PET/CT) in patients with non-thyroidal malignancy.
abstract: BACKGROUND
  Incidental focal fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG) uptake in the thyroid is not uncommon. A significant proportion is due to intercurrent thyroid cancer on further evaluation.
  
  
  OBJECTIVE
  To investigate and discuss the clinical significance and management of incidental focal FDG uptake in the thyroid gland on positron emission tomography/computed tomography (PET/CT) in patients with non-thyroidal malignancy.
  
  
  METHODS
  We investigated 188/7896 (2.4%) patients who had incidental focal thyroid uptake on FDG PET/CT in an oncology population over a 45-month period. Diagnosis was confirmed in 63 patients of whom 59 patients had histopathological verification.
  
  
  RESULTS
  Thirty-two percent of confirmed cases were malignant comprising intercurrent thyroid cancer in three-quarters of these patients. Maximum standardized uptake values of the thyroid lesions and SUV ratios compared with background thyroid and mediastinal uptake were not predictive of a benign or malignant etiology. In patients with incidental thyroid cancers, more than half had non-papillary and intermediate to high-risk pathology.
  
  
  CONCLUSIONS
  Focal FDG uptake in the thyroid gland on PET/CT showed a malignancy risk of 32%. The intensity of uptake does not predict histology and underpins the importance of further investigations to exclude intercurrent thyroid cancer in suitable patients.
authors.affiliation: University of New South Wales, Australia.
authors.forename: Christine
authors.initials: C
authors.lastname: Wong
authors.forename: Michael
authors.initials: M
authors.lastname: Lin
authors.forename: Andrew
authors.initials: A
authors.lastname: Chicco
authors.forename: Rhonda
authors.initials: R
authors.lastname: Benson
mesh_terms: D000368:Aged; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D033162:Incidental Findings; D008297:Male; D049268:Positron-Emission Tomography / Q000379:methods*; D011237:Predictive Value of Tests; D011857:Radiographic Image Interpretation, Computer-Assisted; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D012189:Retrospective Studies; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18