title: Micropapillary histological subtype in lung adenocarcinoma of 2 cm or less: impact on recurrence and clinical predictors.
abstract: OBJECTIVE
  This study examined the clinical and radiological characteristics of adenocarcinoma having the micropapillary histological subtype.
  
  
  METHODS
  We included 233 patients who were operated from 2001 to 2012 for lung adenocarcinoma of 2 cm or less. The pathology was reviewed according to the 2015 WHO classification. We defined adenocarcinoma with a micropapillary component as adenocarcinoma in which the area of the micropapillary histological subtype exceeded 5% of the tumor. The difference in cumulative incidence of recurrence (CIR) in the presence of death as a competing risk between two groups was assessed using the methods of Gray.
  
  
  RESULTS
  Twenty-one cases (9.0%) had a micropapillary component. The micropapillary component was associated with a higher frequency of lymphatic invasion (28.6 vs. 7.5% in adenocarcinoma without a micropapillary component; P = 0.008) and vascular invasion (38.1 vs. 15.1%, P = 0.014) and lymph node metastasis (31.3 vs. 5.2%, P = 0.003). The median follow-up period was 6.5 years. CIR at 5 years was 23.8% [95% confidence interval (CI), 8.3-43.7%] for adenocarcinoma with a micropapillary component, and 11.4% (95% CI, 7.4-16.2%) for adenocarcinoma without a micropapillary component (P = 0.033). Adenocarcinoma with a micropapillary component was more frequent in solid nodules (17.8%, 16/90) on high-resolution computed tomography (HRCT) than in either ground-glass nodules (1.5%, 1/67) or part-solid nodules (5.3%, 4/76) (P = 0.001). The HRCT finding was the only preoperative factor that was associated with a micropapillary component in the multivariate analysis.
  
  
  CONCLUSIONS
  The micropapillary component in adenocarcinoma should be regarded as indicative of a high-grade malignancy and was associated with the HRCT finding.
authors.affiliation: Department of Thoracic Surgery, The University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan. yyoshida-tky@umin.ac.jp.
authors.forename: Yukihiro
authors.identifier: http://orcid.org/0000-0002-6494-2318
authors.initials: Y
authors.lastname: Yoshida
authors.affiliation: Department of Thoracic Surgery, The University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
authors.forename: Jun-Ichi
authors.initials: JI
authors.lastname: Nitadori
authors.affiliation: Department of Pathology, The University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
authors.forename: Aya
authors.initials: A
authors.lastname: Shinozaki-Ushiku
authors.affiliation: Department of Radiology, The University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
authors.forename: Jiro
authors.initials: J
authors.lastname: Sato
authors.affiliation: Department of Clinical Trial Data Management, The University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
authors.forename: Tempei
authors.initials: T
authors.lastname: Miyaji
authors.affiliation: Department of Clinical Trial Data Management, The University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
authors.forename: Takuhiro
authors.initials: T
authors.lastname: Yamaguchi
authors.affiliation: Department of Pathology, The University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Fukayama
authors.affiliation: Department of Thoracic Surgery, The University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Nakajima
mesh_terms: D000230:Adenocarcinoma / Q000175:diagnosis* / Q000601:surgery; D000077192:Adenocarcinoma of Lung; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008175:Lung Neoplasms / Q000175:diagnosis* / Q000601:surgery; D008297:Male; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis*; D009367:Neoplasm Staging; D011013:Pneumonectomy; D011379:Prognosis; D012189:Retrospective Studies; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Lung Neoplasms; Pathology, Surgical; Tomography, X-ray Computed