title: Oncocytic adenomas of thyroid-mimicking benign or metastatic disease on 18F-FDG-PET scan.
abstract: BACKGROUND
  The literature is sparse concerning 18F-fluorodeoxyglucose (18F-FDG) accumulation in the Hürthle cell neoplasm (HCN) of the thyroid. Given the difficulty of accurately diagnosing HCN, even with ultrasound (US) and fine needle aspiration biopsy (FNAB), the ability to accurately characterize these lesions by 18F-FDG positron emission tomography (PET) would be of value.
  
  
  OBJECTIVE
  To describe six cases of oncocytic proliferation in the thyroid gland that mimics the presence of metastatic disease and was detected incidentally by an 18F-FDG PET scan.
  
  
  METHODS
  We conducted whole-body 18F-FDG PET examinations for cancer staging in 1862 oncological patients from 2012 to 2013. Among them, six subjects (4 women, 2 men; age range, 45-85 years) with focal-enhanced 18F-FDG accumulation in the thyroid gland were selected from the study population. This study group was further investigated using 99 m-Tc-pertechnetate scintigraphy, US, and FNAB. Two experienced nuclear physicians reviewed the images. Gray-scale US and color Doppler (CD) sonographic examinations of the thyroid were undertaken for all subjects using a sonographic device Logiq 5 Expert (GE Medical Systems, Osaka, Japan) equipped with a 7-12 MHz linear array transducer.
  
  
  RESULTS
  In all six cases, abnormal 18F-FDG uptake was found locally in the thyroid. The average SUVmax of the HCN was 5.8 (range, 2.6-16). In all six cases, 99 m-Tc-pertechnetate scintigraphy showed a cold spot. Compared with normal parenchymal vascularity, five of the six masses were shown to be hypervascular by CD ultrasonography.
  
  
  CONCLUSIONS
  On PET scans, oncocytic proliferations of the thyroid may mimic metastases of other malignancies. The focal-enhanced uptake of 18F-FDG PET may be associated with a focal increase in the metabolic activity of the thyroid parenchyma due to the presence of oncocytes. Our study emphasizes the importance of obtaining cytological evidence before making a diagnosis of metastatic disease.
authors.affiliation: Institute of Radiology and Nuclear Medicine, Hanusch Hospital, Teaching Hospital of Medical University of Vienna, Austria shahin.zandieh@chello.at.
authors.forename: Shahin
authors.initials: S
authors.lastname: Zandieh
authors.affiliation: Institute of Pathology, Wilhelminenspital, Teaching Hospital of Medical University of Vienna, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Pokieser
authors.affiliation: Institute of Nuclear Medicine with PET-Center, Wilhelminenspital, Teaching Hospital of Medical University of Vienna, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Knoll
authors.affiliation: Institute of Nuclear Medicine with PET-Center, Wilhelminenspital, Teaching Hospital of Medical University of Vienna, Austria.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Sonneck-Koenne
authors.affiliation: Institute of Nuclear Medicine with PET-Center, Wilhelminenspital, Teaching Hospital of Medical University of Vienna, Austria.
authors.forename: Martina
authors.initials: M
authors.lastname: Kudlacek
authors.affiliation: Institute of Nuclear Medicine with PET-Center, Wilhelminenspital, Teaching Hospital of Medical University of Vienna, Austria.
authors.forename: Siroos
authors.initials: S
authors.lastname: Mirzaei
mesh_terms: D018249:Adenoma, Oxyphilic / Q000000981:diagnostic imaging* / Q000556:secondary*; D000368:Aged; D000369:Aged, 80 and over; D003937:Diagnosis, Differential; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000556:secondary*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: 18F-FDG PET; Hürthle cell neoplasm; oncocyic adenoma; oncocytic proliferation thyroid; ultrasound