title: The IASLC Lung Cancer Staging Project: Background Data and Proposed Criteria to Distinguish Separate Primary Lung Cancers from Metastatic Foci in Patients with Two Lung Tumors in the Forthcoming Eighth Edition of the TNM Classification for Lung Cancer.
abstract: It can be difficult to distinguish between a second primary and a metastasis in patients with lung cancer who have more than one pulmonary site of cancer.
  
  
  
  A systematic review of the literature was conducted by a subcommittee of the International Association for the Study of Lung Cancer Staging and Prognostic Factors Committee to develop recommendations to identify second primary lung cancers. The process entailed review of knowledge relating to the mechanism of metastasis, determination of clonality, and outcomes of patients with resected tumors.
  
  
  
  It is easier to determine that two tumors are different than that they are the same; finding similarities does not establish that they are the same. For example, most second primary lung cancers are of the same histotype. Few criteria are reliable by themselves; these include different histologic cancer types or matching DNA breakpoints by sequencing and a comprehensive histologic assessment of resected specimens. Characteristics that are suggestive but associated with potential misclassification include the presence or absence of biomarkers, imaging characteristics, and the presence or absence of nodal involvement.
  
  
  
  Clinical and pathologic (i.e., after resection) criteria are presented to identify two foci as separate primary lung cancers versus a metastasis. Few features are definitive; many commonly used characteristics are suggestive but associated with a substantial rate of misclassification. Careful review by a multidisciplinary tumor board, considering all available information, is recommended.
authors.affiliation: Department of Surgery, Yale University, New Haven, Connecticut. Electronic address: frank.detterbeck@yale.edu.
authors.forename: Frank C
authors.initials: FC
authors.lastname: Detterbeck
authors.affiliation: Department of Pathology, University of Colorado, Denver, Colorado.
authors.forename: Wilbur A
authors.initials: WA
authors.lastname: Franklin
authors.affiliation: Department of Histopathology, Royal Brompton and Harefield National Health Service Foundation Trust and Imperial College, London, United Kingdom.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Nicholson
authors.affiliation: Respiratory Medicine Service, Hôpital Louis Pradel, Hospices Civils de Lyon, Lyon, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Girard
authors.affiliation: Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan.
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Arenberg
authors.affiliation: Department of Pathology, Sloan-Kettering Cancer Center, New York, New York.
authors.forename: William D
authors.initials: WD
authors.lastname: Travis
authors.affiliation: Department of Internal Medicine, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Mazzone
authors.affiliation: Department of Diagnostic Imaging, Tel-Aviv University, Ramat Gan, Israel.
authors.forename: Edith M
authors.initials: EM
authors.lastname: Marom
authors.affiliation: Department of Thoracic Surgery, New York University, New York, New York.
authors.forename: Jessica S
authors.initials: JS
authors.lastname: Donington
authors.affiliation: Department of Internal Medicine, Yale University, New Haven, Connecticut.
authors.forename: Lynn T
authors.initials: LT
authors.lastname: Tanoue
authors.affiliation: Thoracic Surgery Service, Sloan-Kettering Cancer Center, New York, New York.
authors.forename: Valerie W
authors.initials: VW
authors.lastname: Rusch
authors.affiliation: Division of Thoracic Surgery, Keio University, School of Medicine, Tokyo, Japan.
authors.forename: Hisao
authors.initials: H
authors.lastname: Asamura
authors.affiliation: Thoracic Surgery Service, Hospital Universitari Mutua Terrassa, Barcelona, Spain; Centros de Investigación Biomédica en Red de Enfermedades Respiratorias (CIBERES) Lung Cancer Group, Terrassa, Barcelona, Spain.
authors.forename: Ramón
authors.initials: R
authors.lastname: Rami-Porta
mesh_terms: D000230:Adenocarcinoma / Q000145:classification* / Q000556:secondary; D006801:Humans; D008175:Lung Neoplasms / Q000145:classification* / Q000473:pathology; D015201:Meta-Analysis as Topic; D009367:Neoplasm Staging / Q000592:standards*; D016609:Neoplasms, Second Primary / Q000145:classification* / Q000473:pathology; D011379:Prognosis
keywords: Lung cancer; Lung cancer staging; Multiple tumors; Non–small cell lung cancer; TNM classification