title: Systematic review: prevalence of malignant incidental thyroid nodules identified on fluorine-18 fluorodeoxyglucose positron emission tomography.
abstract: OBJECTIVE
  To review current literature and determine the prevalence of malignant incidental focal hypermetabolic thyroid lesions detected by fluorine-18 fluorodeoxyglucose positron emission tomography (F-FDG-PET).
  
  
  METHODS
  Studies evaluating thyroid carcinomas discovered incidentally on F-FDG-PET were systematically searched in the MEDLINE, CINAHL, and Evidence-Based Medicine (EBM) Reviews from 1998 to 2007. Studies were eligible for inclusion with the following criteria: F-FDG-PET studies carried out on humans, long-term clinical follow-up or presence of histological confirmation of thyroid disease, and if studies reported the prevalence of abnormal F-FDG-PET scans with thyroid lesions and confirmed pathological thyroid disease. Studies were excluded if (1) there was no confirmed diagnosis, (2) there was a history of thyroid cancer, (3) they were carried out for diagnoses of thyroid abnormalities, or (4) they were case series. Two reviewers independently reviewed each study's eligibility and abstracted the data.
  
  
  RESULTS
  Eighteen articles met criteria resulting in a total of 55 160 patients with 571 patients (1%) having an unexpected focal abnormality in the thyroid gland. Diagnostic confirmations were obtained in 322 patients. Among the confirmed diagnoses, 200 (62.1%) were benign, 107 (33.2%) were malignant, and 15 (4.7%) were indeterminate or a patient without a clear diagnosis. Papillary thyroid carcinoma was the most prevalent thyroid malignancy (82.2%). Eight studies reporting individual maximum standard uptake values were included in a subanalysis. The mean maximum standard uptake value for 73 benign lesions was 4.6+/-2.1, and for the 52 malignant lesions was 6.8+/-4.6 (P<0.001).
  
  
  CONCLUSIONS
  The high prevalence of malignancy associated with focal hypermetabolic thyroid nodules found on F-FDG-PET warrants further evaluation when detected.
authors: Diagnostic Imaging Services, Kaiser Permanente Fontana Medical Center, Fontana, California, USA. philip.shie@kp.org
authors: Philip
authors: P
authors: Shie
authors: Roberto
authors: R
authors: Cardarelli
authors: Kelly
authors: K
authors: Sprawls
authors: Kimberly G
authors: KG
authors: Fulda
authors: Alan
authors: A
authors: Taur
mesh_terms: D019788:Fluorodeoxyglucose F18; D006801:Humans; D033162:Incidental Findings; D049268:Positron-Emission Tomography; D016606:Thyroid Nodule / Q000175:diagnosis* / Q000000981:diagnostic imaging
chemical_list: D019788:Fluorodeoxyglucose F18