title: ¹⁸F-fluorodeoxyglucose PET/CT findings in pleural effusions of patients with known cancer. A cytopathological correlation.
abstract: OBJECTIVE
  Pleural effusion is common in cancer patients and to determine its malignant origin is of huge clinical significance. PET/CT with ¹⁸F-FDG is of diagnostic value in staging and follow-up, but its ability to differentiate between malignant and benign effusions is not precisely known.
  
  
  METHODS
  We examined 50 PET/CT from 47 patients (29 men, 18 women, 60 ± 16 years) with pleural effusion and known cancer (24 NSCLC, 7 lymphomas, 5 breasts, 4 GIST, 3 mesotheliomas, 2 head and neck, 2 malignant teratoma, 1 colorectal, 1 oesophageal, 1 melanoma) for FDG uptake in the effusions using SUV(max). This was correlated to cytopathology performed after a median of 21 days (interquartile range -3 to 23), which included pH, relative distribution (macrophages, neutrophils, eosinophils, basophils, lymphocytes, plasmocytes), and absolute cell count.
  
  
  RESULTS
  Malignant cells were found in 17 effusions (34%) (6 NSCLC, 5 lymphomas, 2 breasts, 2 mesotheliomas, 2 malignant teratomas). SUV in malignant effusions were higher than in benign ones [3.7 (95%CI 1.8-5.6) vs. 1.7 g/ml (1.5-1.9), p = 0.001], with a correlation between malignant effusion and SUV (Spearman coefficient r = 0.50, p = 0.001), but not with other cytopathological or radiological parameters (ROC area 0.83 ± 0.06). Using a 2.2-mg/l SUV threshold, 12 PET/CT studies were positive and 38 negative with sensitivity, specificity, positive and negative predictive values of 53%, 91%, 75% and 79%, respectively. For NSCLC only (n = 24), ROC area was 0.95 ± 0.04, 7 studies were positive and 17 negative with a sensitivity, specificity, positive and negative predictive values of 83%, 89%, 71 and 94%, respectively.
  
  
  CONCLUSIONS
  PET/CT may help to differentiate the malignant or benign origin of a pleural effusion with a high specificity in patients with known cancer, in particular NSCLC.
authors.affiliation: University Institute of Pathology, Lausanne University Hospital, Switzerland.
authors.forename: I
authors.initials: I
authors.lastname: Letovanec
authors.forename: G
authors.initials: G
authors.lastname: Allenbach
authors.forename: A
authors.initials: A
authors.lastname: Mihaescu
authors.forename: M
authors.initials: M
authors.lastname: Nicod Lalonde
authors.forename: S
authors.initials: S
authors.lastname: Schmidt
authors.forename: R
authors.initials: R
authors.lastname: Stupp
authors.forename: J-W
authors.initials: JW
authors.lastname: Fitting
authors.forename: A
authors.initials: A
authors.lastname: Boubaker
authors.forename: H-B
authors.initials: HB
authors.lastname: Ris
authors.forename: J O
authors.initials: JO
authors.lastname: Prior
mesh_terms: D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D009369:Neoplasms / Q000150:complications* / Q000175:diagnosis*; D010996:Pleural Effusion / Q000175:diagnosis* / Q000209:etiology*; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18