title: Differentiation between malignancy and inflammation in pulmonary ground-glass nodules: The feasibility of integrated (18)F-FDG PET/CT.
abstract: BACKGROUND
  (18)F-FDG PET/CT has been used to differentiate malignant solid lung nodules from benign nodules. We assess the feasibility of integrated (18)F-FDG PET/CT for the differentiation of malignancy from inflammation manifested as ground-glass nodules (GGNs) on chest CT.
  
  
  METHODS
  A total of 68 GGNs in 45 patients (M:F=24:21; mean age, 61) fulfilled the following criteria: (a) nodules composed of >/=50% ground-glass opacity, (b) patients who underwent integrated PET/CT within 1 week following dedicated chest CT, (c) definitive diagnosis determined by pathological specimen or at least 9 months of follow-up, and (d) lesions >/=10mm in diameter. 36 malignant GGNs were pathologically proved as adenocarcinoma (n=20), bronchioloalveolar carcinoma (n=11), low-grade lymphoma (n=3), metastatic mucinous adenocarcinoma (n=1) and unknown low-grade malignancy (n=1). 32 inflammatory GGNs were confirmed as pneumonic infiltration as they had disappeared on follow-up CT and were associated with compatible clinical features (n=26) or as chronic inflammation with fibrosis by VATS biopsy (n=6). Using CT density histogram analysis, 14 were classified as pure GGNs and 54 as part-solid nodules. Integrated PET/CT was evaluated by measuring the maximum standardized uptake value (SUV) at the region of interest located at each lesion. The Mann-Whitney U test was performed to compare the SUV of malignancy and inflammation. The optimal cut-off value of SUV to differentiate malignancy from inflammation was determined using a receiver operating characteristic-based positive test. Sensitivity, specificity, accuracy, and positive predictive values (PPV) and negative predictive values (NPV) were calculated at the level of the optimal cut-off value. SUV showing 100% PPV for inflammatory GGNs was evaluated.
  
  
  RESULTS
  In part-solid nodules, the maximum SUV was significantly higher in inflammation (2.00+/-1.18; range, 0.48-5.60) than in malignancy (1.26+/-0.71; range, 0.32-2.6) (P=0.018). On the other hand, in pure GGNs, the maximum SUV of malignancy (0.64+/-0.19; range, 0.43-0.96) and inflammation (0.74+/-0.28; range, 0.32-1.00) showed no difference (P=0.37). Using the optimal cut-off value of SUV as 1.2 (P=0.01) sensitivity, specificity, accuracy, PPV and NPV in part-solid nodules were 62.1%, 80.0%, 70.4%, 78.3% and 64.5%, respectively. Six part-solid nodules, which showed a maximum SUV of higher than 2.6, were all inflammations.
  
  
  CONCLUSIONS
  The part-solid nodules with positive FDG-PET could be inflammatory nodules rather than malignant nodules. This is a quite paradoxical result when considering the basic knowledge that malignant pulmonary nodules have higher glucose metabolism.
authors.affiliation: Department of Radiology, Seoul National University Bundang Hospital, Republic of Korea.
authors.forename: Eun Ju
authors.initials: EJ
authors.lastname: Chun
authors.forename: Hyun Ju
authors.initials: HJ
authors.lastname: Lee
authors.forename: Won Jun
authors.initials: WJ
authors.lastname: Kang
authors.forename: Kwang Gi
authors.initials: KG
authors.lastname: Kim
authors.forename: Jin Mo
authors.initials: JM
authors.lastname: Goo
authors.forename: Chang Min
authors.initials: CM
authors.lastname: Park
authors.forename: Chang Hyun
authors.initials: CH
authors.lastname: Lee
mesh_terms: D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007249:Inflammation / Q000000981:diagnostic imaging / Q000473:pathology; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D003074:Solitary Pulmonary Nodule / Q000000981:diagnostic imaging* / Q000473:pathology; D014057:Tomography, X-Ray Computed
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18