title: Efficacy of conventional whole-body ¹⁸F-FDG PET/CT in the incidental findings of parotid masses.
abstract: OBJECTIVE
  The objective of this study was to evaluate the incidence of incidental parotid masses with conventional whole-body ¹⁸F-deoxyglucose (FDG) PET/CT and assess the ability of PET/CT to characterize these unexpected parotid lesions.
  
  
  METHODS
  Fifty eight incidental findings of parotid masses with routine FDG PET/CT whole-body scan were reviewed in this retrospective analysis, which were selected from the patients without any known or suspected parotid disease in our PET center, from June 2005 to May 2009. 51 cases were operated or underwent a biopsy after a short-term PET/CT study; the remaining 7 cases had a follow-up. Parotid mass that showed both noncontrast CT (irregular shape and blurry border) and PET malignant features (high FDG uptake, SUV(max) > 3.0) was considered as positive for malignancy. Correlation of FDG PET/CT with histology or follow-up outcome was performed.
  
  
  RESULTS
  Fifty eight unexpected findings of parotid masses accounted for 0.3% of the total cases in 4 years, including 11 (19.0%) malignant tumors and 47 (81.0%) benign lesions. 13 lesions manifested single nodule with malignant CT features and intense FDG activity, of which 6 were proved to be malignant; thus, sensitivity and positive predictive values were 54.5% (6 of 11) and 46.2% (6 of 13), respectively. 45 lesions showed either single nodule with benign CT features, or a low FDG uptake (SUV(max) ≤ 3.0), of which 40 were true negatives; therefore, specificity and negative predictive values were 85.1% (40 of 47) and 88.9% (40 of 45), respectively. All parotid masses except 9 benign and 1 malignant showed a high FDG uptake. Compared with SUV only, combined interpretation of PET and CT results displayed a lower sensitivity (90.9-54.5%), but a higher specificity (19.1-85.1%) and a higher overall accuracy.
  
  
  CONCLUSIONS
  Whole-body FDG-PET/CT at the time of surveying the entire body condition is helpful for detecting the asymptomatic parotid masses. Combined noncontrast CT is an essential evidence for improving the diagnostic accuracy of FDG-PET/CT for parotid masses.
authors.affiliation: PET Center, Huashan Hospital, Fudan University, Shanghai, China. huihui_0316@163.com
authors.forename: Hui-Chun
authors.initials: HC
authors.lastname: Wang
authors.forename: Chuan-Tao
authors.initials: CT
authors.lastname: Zuo
authors.forename: Feng-Chun
authors.initials: FC
authors.lastname: Hua
authors.forename: Zhe-Min
authors.initials: ZM
authors.lastname: Huang
authors.forename: Hai-Bo
authors.initials: HB
authors.lastname: Tan
authors.forename: Jun
authors.initials: J
authors.lastname: Zhao
authors.forename: Yi-Hui
authors.initials: YH
authors.lastname: Guan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D006801:Humans; D033162:Incidental Findings; D008297:Male; D008875:Middle Aged; D010307:Parotid Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D049268:Positron-Emission Tomography; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D051598:Whole Body Imaging; D055815:Young Adult
chemical_list: D019788:Fluorodeoxyglucose F18