title: Detection of unknown occult primary tumors using positron emission tomography.
abstract: BACKGROUND
  The potential of positron emission tomography (PET) with 18F-fluoro-2-deoxy-D-glucose (FDG) to detect primary tumors after unsuccessful conventional diagnostic workup was assessed in patients with metastatic disease from an unknown primary tumor.
  
  
  METHODS
  Twenty-nine patients with various histologic types of metastases from an unknown primary site were studied after unsuccessful conventional diagnostic workup. The patients received 370 megabecquerels (MBq) (10 millicuries) FDG intravenously and whole body scans were made after 30 minutes after injection onward.
  
  
  RESULTS
  All but one known metastatic tumor sites were visualized. Additional metastases were discovered in five patients. With FDG-PET the primary tumor was identified in 7 patients (24%): in 2 patients with carcinoma of the nasopharynx, in 1 patient with plasmacytoma of the base of the tongue, in 1 patient with carcinoma of the lung, in 1 patient with carcinoma of the colon, and in 2 patients with breast carcinoma. FDG-PET did not identify a primary tumor in the remaining 22 patients (76%). Despite a negative PET study, the primary lesion was identified in a later phase in 3 of these patients (14%). Survival was not altered by discovery of the primary tumor.
  
  
  CONCLUSIONS
  A previously unknown primary tumor was able to be identified with FDG-PET in 7 of 29 patients after an unsuccessful conventional diagnostic workup. However, the clinical relevance of PET information in this setting is limited.
authors.affiliation: PET Center, Department of Surgical Oncology, Groningen University Hospital, The Netherlands.
authors.forename: A C
authors.initials: AC
authors.lastname: Kole
authors.forename: O E
authors.initials: OE
authors.lastname: Nieweg
authors.forename: J
authors.initials: J
authors.lastname: Pruim
authors.forename: H J
authors.initials: HJ
authors.lastname: Hoekstra
authors.forename: H S
authors.initials: HS
authors.lastname: Koops
authors.forename: J L
authors.initials: JL
authors.lastname: Roodenburg
authors.forename: W
authors.initials: W
authors.lastname: Vaalburg
authors.forename: A
authors.initials: A
authors.lastname: Vermey
mesh_terms: D000328:Adult; D000368:Aged; D001859:Bone Neoplasms / Q000556:secondary; D001932:Brain Neoplasms / Q000556:secondary; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009382:Neoplasms, Unknown Primary / Q000000981:diagnostic imaging*; D019275:Radiopharmaceuticals; D012878:Skin Neoplasms / Q000556:secondary; D014055:Tomography, Emission-Computed
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18