title: Pulmonary nodular ground-glass opacities in patients with extrapulmonary cancers: what is their clinical significance and how can we determine whether they are malignant or benign lesions?
abstract: BACKGROUND
  The clinical significance of pulmonary nodular ground-glass opacities (NGGOs) in patients with extrapulmonary cancers is not known, although there is an urgent need for study on this topic. The purpose of this study, therefore, was to investigate the clinical significance of pulmonary NGGOs in these patients, and to develop a computerized scheme to distinguish malignant from benign NGGOs.
  
  
  METHODS
  Fifty-nine pathologically proven pulmonary NGGOs in 34 patients with a history of extrapulmonary cancer were studied. We reviewed the CT scan characteristics of NGGOs and the clinical features of these patients. Artificial neural networks (ANNs) were constructed and tested as a classifier distinguishing malignant from benign NGGOs. The performance of ANNs was evaluated with receiver operating characteristic analysis.
  
  
  RESULTS
  Twenty-eight patients (82.4%) were determined to have malignancies. Forty NGGOs (67.8%) were diagnosed as malignancies (adenocarcinomas, 24; bronchioloalveolar carcinomas, 16). Among the rest of the NGGOs, 14 were atypical adenomatous hyperplasias, 4 were focal fibrosis, and 1 was an inflammatory nodule. There were no cases of metastasis appearing as NGGOs. Between malignant and benign NGGOs, there were significant differences in lesion size; the presence of internal solid portion; the size and proportion of the internal solid portion; the lesion margin; and the presence of bubble lucency, air bronchogram, or pleural retraction (p < 0.05). Using these characteristics, ANNs showed excellent accuracy (z value, 0.973) in discriminating malignant from benign NGGOs.
  
  
  CONCLUSIONS
  Pulmonary NGGOs in patients with extrapulmonary cancers tend to have high malignancy rates and are very often primary lung cancers. ANNs might be a useful tool in distinguishing malignant from benign NGGOs.
authors.affiliation: Departments of Radiology, Seoul National University College of Medicine, Seoul, South Korea.
authors.forename: Chang Min
authors.initials: CM
authors.lastname: Park
authors.affiliation: Departments of Radiology, Seoul National University College of Medicine, Seoul, South Korea. Electronic address: jmgoo@plaza.snu.ac.kr.
authors.forename: Jin Mo
authors.initials: JM
authors.lastname: Goo
authors.affiliation: Departments of Radiology, Seoul National University College of Medicine, Seoul, South Korea.
authors.forename: Tae Jung
authors.initials: TJ
authors.lastname: Kim
authors.affiliation: Departments of Radiology, Seoul National University College of Medicine, Seoul, South Korea.
authors.forename: Hyun Ju
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: Departments of Radiology, Seoul National University College of Medicine, Seoul, South Korea.
authors.forename: Kyung Won
authors.initials: KW
authors.lastname: Lee
authors.affiliation: Departments of Radiology, Seoul National University College of Medicine, Seoul, South Korea.
authors.forename: Chang Hyun
authors.initials: CH
authors.lastname: Lee
authors.affiliation: Thoracic and Cardiovascular Surgery, Seoul National University College of Medicine, Seoul, South Korea.
authors.forename: Young Tae
authors.initials: YT
authors.lastname: Kim
authors.affiliation: Department of Biomedical Engineering, Division of Basic & Applied Sciences, National Cancer Center, Gyeonggi-Do, South Korea.
authors.forename: Kwang Gi
authors.initials: KG
authors.lastname: Kim
authors.affiliation: Departments of Radiology, Seoul National University College of Medicine, Seoul, South Korea.
authors.forename: Ho Yun
authors.initials: HY
authors.lastname: Lee
authors.affiliation: Departments of Radiology, Seoul National University College of Medicine, Seoul, South Korea.
authors.forename: Eun-Ah
authors.initials: EA
authors.lastname: Park
authors.affiliation: Departments of Radiology, Seoul National University College of Medicine, Seoul, South Korea.
authors.forename: Jung-Gi
authors.initials: JG
authors.lastname: Im
mesh_terms: D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000145:classification / Q000000981:diagnostic imaging / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D016609:Neoplasms, Second Primary / Q000145:classification / Q000473:pathology*; D016571:Neural Networks, Computer; D012372:ROC Curve; D011859:Radiography; D012189:Retrospective Studies; D003074:Solitary Pulmonary Nodule / Q000145:classification / Q000000981:diagnostic imaging* / Q000473:pathology