title: Positron emission tomography: poor sensitivity for occult tonsillar cancer.
abstract: OBJECTIVE
  The aim of the study was to determine the sensitivity of preoperative positron emission tomography (PET) scans in the detection of primary tumors of the tonsils.
  
  
  METHODS
  We conducted a retrospective review of 46 patients treated at a university medical center for occult tonsillar cancer during the years 2002 to 2004. We identified patients who underwent a preoperative PET scan to locate an unknown primary tumor. Fusion computed tomography with PET (PET/CT) was used to further delineate anatomic localization to the tonsil area. A positive PET/CT scan was defined as asymmetric increased tracer uptake in the tonsil and/or tonsillar fossa ipsilateral to the tonsillar cancer site when compared with the contralateral site. A negative PET/CT scan was defined as equivocal symmetric tracer uptake bilaterally.
  
  
  RESULTS
  Of the 46 patients, 6 (13.0%) had pretreatment PET scans. Of these 6 patients, 16.7% (n = 1) had positive PET, 66.7% (n = 4) had negative PET, and 16.7% (n = 1) demonstrated increased tracer uptake in tonsils bilaterally greater on the side contralateral to the cancer. In this group, PET scans had a sensitivity of 0.167 and false-negative ratio of 0.667 for tonsillar cancer detection.
  
  
  CONCLUSIONS
  Although the patient population in this study is small (n = 6), the findings suggest that PET/ CT scans may offer a low sensitivity in detection of primary tonsillar cancers. However, PET/CT scans still have a significant role in the detection of other unknown primary head and neck tumors. Technical reasons for this finding are discussed.
authors.affiliation: Division of Head and Neck Surgery-Otolaryngology, David Geffen School of Medicine at the University of California, Los Angeles, Los Angeles, CA 90095, USA. vnabili@ucla.edu <vnabili@ucla.edu>
authors.forename: Vishad
authors.initials: V
authors.lastname: Nabili
authors.forename: Brita
authors.initials: B
authors.lastname: Zaia
authors.forename: Keith E
authors.initials: KE
authors.lastname: Blackwell
authors.forename: Christian S
authors.initials: CS
authors.lastname: Head
authors.forename: Karsten
authors.initials: K
authors.lastname: Grabski
authors.forename: Joel A
authors.initials: JA
authors.lastname: Sercarz
mesh_terms: D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D006801:Humans; D008223:Lymphoma / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D009382:Neoplasms, Unknown Primary / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography; D011300:Preoperative Care; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed; D014067:Tonsillar Neoplasms / Q000000981:diagnostic imaging*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18