title: A decrease in the size of ground glass nodules may indicate the optimal timing for curative surgery.
abstract: OBJECTIVE
  Although ground glass nodules (GGNs) are generally considered to grow slowly to a large size, their natural progression remains unclear, and a decrease in tumor size has been reported in a few previous studies. The study aimed to retrospectively review the radiologic and pathological characteristics of resected ground glass nodules (GGNs) followed with chest computed tomography (CT) for at least a year before surgery to clarify the natural progression of GGNs.
  
  
  METHODS
  The chest CT cans and clinical charts of 32 GGNs in 31 patients who underwent pulmonary resection between January 2006 and March 2013 were retrospectively reviewed. The definitions of pure GGNs and part-solid nodules were based on the tumor shadow disappearance rate. The tumor size was measured twice, and the mean size was used for evaluation.
  
  
  RESULTS
  The mean GGN size before surgery was 15.2 mm, and the median follow-up period before surgery was 21 months. In the follow-up period, 15 (58%) of 26 pure GGNs at the initial CT remained pure GGNs at the last CT. However, a solid component appeared in the remaining 11 tumors (42%) of the 26 initial pure GGNs. Furthermore, 1 GGN of the 15 GGNs that remained pure and 10 of the 11 GGNs with solid component also showed a size decrease. In addition, 6 part-solid nodules were observed at the initial CT. Of these, 3 showed a decrease in size during follow-up. Overall, 47% of the GGNs showed a size reduction on follow-up chest CT.
  
  
  CONCLUSIONS
  A size reduction was observed in nearly half of the GGNs and suggested the progression to an invasive adenocarcinoma. When a mild collapse of the GGNs is observed, a careful follow-up is necessary to identify a solid component. Tumor size decreases may represent the optimal timing of pulmonary resection for curative treatment.
authors.affiliation: Division of Thoracic Surgery, Kansai Medical University Hirakata Hospital, Japan; Department of Thoracic and Cardiovascular Surgery, Kansai Medical University, Osaka, Japan. Electronic address: kanedah@hirakata.kmu.ac.jp.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kaneda
authors.affiliation: Division of Thoracic Surgery, Kansai Medical University Hirakata Hospital, Japan; Department of Thoracic and Cardiovascular Surgery, Kansai Medical University, Osaka, Japan.
authors.forename: Takahito
authors.initials: T
authors.lastname: Nakano
authors.affiliation: Division of Thoracic Surgery, Kansai Medical University Hirakata Hospital, Japan; Department of Thoracic and Cardiovascular Surgery, Kansai Medical University, Osaka, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Taniguchi
authors.affiliation: Division of Thoracic Surgery, Kansai Medical University Hirakata Hospital, Japan; Department of Thoracic and Cardiovascular Surgery, Kansai Medical University, Osaka, Japan.
authors.forename: Tomohito
authors.initials: T
authors.lastname: Saito
authors.affiliation: Division of Thoracic Surgery, Kansai Medical University Hirakata Hospital, Japan; Department of Thoracic and Cardiovascular Surgery, Kansai Medical University, Osaka, Japan.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Konobu
authors.affiliation: Division of Thoracic Surgery, Kansai Medical University Hirakata Hospital, Japan; Department of Thoracic and Cardiovascular Surgery, Kansai Medical University, Osaka, Japan.
authors.forename: Yukihito
authors.initials: Y
authors.lastname: Saito
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012189:Retrospective Studies; D003074:Solitary Pulmonary Nodule / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000601:surgery; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden
keywords: Adenocarcinoma; Computed tomography; Curative surgery; Ground glass nodules; Non-small cell lung cancer; Optimal timing