title: Occult malignancy in patients with suspected paraneoplastic neurologic syndromes: value of positron emission tomography in diagnosis.
abstract: OBJECTIVE
  To determine the value of positron emission tomography (PET) in diagnosing occult malignancies in patients with paraneoplastic neurologic syndromes (PNSs) at Mayo Clinic's site in Rochester, MN.
  
  
  METHODS
  We retrospectively reviewed the medical charts of all 107 patients who underwent PET from January 1, 2000, to July 31, 2006, for the indication of suspected PNS. Three patients did not meet inclusion criteria. PET results were considered positive if increased fludeoxyglucose F 18 uptake indicated malignancy (24 patients). Results from computed tomography were interpreted as positive if any suspect lesion was consistent with malignancy (26 patients).
  
  
  RESULTS
  One hundred four patients with PNS were identified from the PET central database; 73 patients had at least 1 positive result for paraneoplastic antibody, and 31 had antibody-negative PNS. Malignancy was confirmed pathologically in 10 patients, of whom 8 had positive PET results. There were 2 cases of confirmed malignancy (fallopian tube adenocarcinoma and spindle cell uterine carcinoma) for which PET results were negative. Two patients with positive PET results declined biopsy. Computed tomography was able to identify 3 of the 10 malignancies detected. Five cases of malignancy were detected only by PET. All patients with confirmed malignancy had positive results for at least 1 paraneoplastic antibody. One patient with positive results for PNS antibody and negative PET results was diagnosed as having small cell carcinoma on a follow-up PET scan after 27 months. PET had sensitivity, specificity, positive predictive value, and negative predictive value of 80%, 67%, 53%, and 88%, respectively.
  
  
  CONCLUSIONS
  PET scan was shown to be more sensitive than computed tomography for detecting occult malignancy (confirmed by positive test results for autoantibody) among patients with suspected PNS. The greatest clinical utility of PET could be in its high negative predictive value.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA.
authors.forename: Rajesh R
authors.initials: RR
authors.lastname: Patel
authors.forename: Rathan M
authors.initials: RM
authors.lastname: Subramaniam
authors.forename: Jaywant N
authors.initials: JN
authors.lastname: Mandrekar
authors.forename: Julie E
authors.initials: JE
authors.lastname: Hammack
authors.forename: Val J
authors.initials: VJ
authors.lastname: Lowe
authors.forename: James R
authors.initials: JR
authors.lastname: Jett
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000912:Antibodies, Neoplasm / Q000032:analysis; D003937:Diagnosis, Differential; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D020361:Paraneoplastic Syndromes, Nervous System / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D000912:Antibodies, Neoplasm; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18