title: Modified histologic classification as a prognostic factor in pulmonary adenocarcinoma.
abstract: BACKGROUND
  The histologic pattern of pulmonary adenocarcinoma is highly heterogeneous and considered to be an important prognostic factor. The predominant histologic pattern is emphasized in the 2011 International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society classification, but few studies present a detailed investigation of the histologic changes and prognosis pulmonary adenocarcinoma using resected specimens.
  
  
  METHODS
  We examined 125 cases of surgically resected pulmonary adenocarcinoma and carefully observed histologic patterns. Invasive adenocarcinoma was divided into 3 groups according to a modified histologic classification system: group 1 had a lepidic or papillary predominant pattern with ≤10% solid or micropapillary pattern; group 2 had an acinar predominant pattern with ≤10% of the solid or micropapillary pattern; and group 3 had a solid or micropapillary predominant pattern, or any predominant pattern with >10% solid or micropapillary pattern.
  
  
  RESULTS
  Proportions of predominant lepidic, papillary, acinar, solid, and micropapillary patterns were 11 (9.3%), 8 (6.8%), 54 (45.8%), 38 (32.2%), and 7 (5.9%), respectively. Vague areas between 2 different patterns were frequently observed, which were considered as transitional areas for one pattern to the other pattern (gradual dedifferentiation). Modified histologic classification was significantly associated with disease-free and overall survival rate (P = .026 and .010, respectively) using the Kaplan-Meier survival test, and an independent prognostic factor (P = .016) in overall survival using the Cox regression test.
  
  
  CONCLUSIONS
  Pulmonary adenocarcinoma demonstrates heterogeneous histologic patterns with gradual dedifferentiation, and this modified histologic classification is an important prognostic factor for patients with pulmonary adenocarcinoma.
authors.affiliation: 1Department of Pathology, Keimyung University School of Medicine, Daegu, Korea.
authors.forename: Ilseon
authors.initials: I
authors.lastname: Hwang
authors.forename: Keon Uk
authors.initials: KU
authors.lastname: Park
authors.forename: Kun Young
authors.initials: KY
authors.lastname: Kwon
mesh_terms: D000230:Adenocarcinoma / Q000145:classification* / Q000401:mortality* / Q000473:pathology*; D000077192:Adenocarcinoma of Lung; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008175:Lung Neoplasms / Q000145:classification* / Q000401:mortality* / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D016016:Proportional Hazards Models
keywords: adenocarcinoma; gradual dedifferentiation; histologic pattern; lung; prognosis