Rudolf M. Huber, Hisao Asamura, Wilbur A. Franklin, Kim R. Geisinger, M. Tsao, James R. Jett, Bruce E. Johnson, Douglas W. Henderson, Denise R. Aberle, David A Johnson, Rafael Rosell, Ignacio I. Wistuba, Keiko Kuriyama, William D. Travis, Valerie W. Rusch, Victor L. Roggli, Jean-Paul Sculier, Fred R. Hirsch, Paul Van Schil, Douglas B. Flieder, Jin Soo Lee, Keith M. Kerr, Andrew G. Nicholson, Elisabeth Brambilla, Nagahiro Saijo, Yasushi Yatabe, Yuichi Ishikawa, Vincent A. Miller, John H. M. Austin, Christian Brambilla, Masayuki Noguchi, Gregory J. Riely, Iver Petersen, Charles A. Powell, Michael K. Gould, David G. Beer, David Yankelewitz, Masahiro Tsuboi, Kavita Garg, Pan-Chyr Yang, Montserrat Sanchez-Cespedes, Tetsuya Mitsudomi, Philip S. Hasleton, Johan Vansteenkiste, Takashi Takahashi, Erik Thunnissen, Adi F. Gazdar, Giorgio V. Scagliotti, Department of Pathology, Memorial Sloane Kettering Cancer Center [New York], Département d'anatomie et cythologie pathologique, CHU Grenoble-Hôpital Michallon, Université de Tsukuba = University of Tsukuba, Department of histopathology, Royal Brompton Hospital-National Heart and Lung Institute Division of Imperial College School of Medicine, Wake Forest Univ./Medicine Medical Center, Department of Pathology and Molecular Diagnostics, Aichi Cancer Ctr., University of Michigan [Ann Arbor], University of Michigan System, Columbia University [New York], Thoracic Oncology Service, University of Antwerp (UA), Department of Radiology, University of Colorado Anschutz [Aurora], Department of Thoracic Surgery, National Cancer Centre, University of Colorado Cancer Center, University of Colorado [Denver], Department of Thoracic Oncology, Università degli studi di Torino (UNITO)-San Luigi Hospital, Aichi Cancer Center Hospital, Pneumologie, University of Munich, The JFCR Cancer Institute, Oncology and Pulmonary and Critical Care Medicine, Mayo Clinic, Institut d' Investigacions Biomediques Bellvitge (IDIBELL), Programa de Epigenètica y Biología del Cáncer-PEBC, Department of Medicine, Institut Jules Bordet [Bruxelles], Faculté de Médecine [Bruxelles] (ULB), Université libre de Bruxelles (ULB)-Université libre de Bruxelles (ULB)-Faculté de Médecine [Bruxelles] (ULB), Université libre de Bruxelles (ULB)-Université libre de Bruxelles (ULB), Div. of Molecular Carcinogenesis, Nagoya University, Tokyo Medical University, Department of Pulmonology, University Hospitals Leuven [Leuven], Departments of Pathology and Thoracic/Head and Neck Medical Oncology, The University of Texas M.D. Anderson Cancer Center [Houston], Department of Internal Medicine, National Taiwan University College of Medicine, University of California [Los Angeles] (UCLA), University of California-University of California, INSERM U823, équipe 2 (Bases Moléculaires de la Progression des Cancers du Poumon), Institut d'oncologie/développement Albert Bonniot de Grenoble (INSERM U823), Université Joseph Fourier - Grenoble 1 (UJF)-CHU Grenoble-EFS-Institut National de la Santé et de la Recherche Médicale (INSERM)-Université Joseph Fourier - Grenoble 1 (UJF)-CHU Grenoble-EFS-Institut National de la Santé et de la Recherche Médicale (INSERM)-Clinique de pneumologie, CHU Grenoble, Fox Chase Cancer Center, UCHSC at Fitzsimons, The University of Texas Health Science Center at Houston (UTHealth), Pulmonary Medicine, Dept of Histopathology, Central Manchester University Hospital, Flinders Medical Centre, Dana-Farber Cancer Institute [Boston], University of Texas Southwestern Medical Center [Dallas], Aberdeen University Medical School, National Hospital Organization Osaka National Hospital, National Cancer Center Korea, Institute of pathology, Universitätsklinikum Friedrich-Schiller-University (FSU), Friedrich-Schiller-Universität = Friedrich Schiller University Jena [Jena, Germany]-Friedrich-Schiller-Universität = Friedrich Schiller University Jena [Jena, Germany], Medical Center [Durham], Duke University [Durham], Medical Oncology Service, Catalan Institute of Oncology, Medical Oncology Division, Kinki/Kindai University School of Medicine, Kindai University-Kindai University, VU Medical Center, Princess Margaret Hospital, University of Toronto-University of Toronto, Weill Medical College of Cornell University [New York], Pathology, CCA - Oncogenesis, Brambilla, Christian, Università degli studi di Torino = University of Turin (UNITO)-San Luigi Hospital, and University of California (UC)-University of California (UC)
Introduction: Adenocarcinoma is the most common histologic type of lung cancer. To address advances in oncology, molecular biology, pathology, radiology, and surgery of lung adenocarcinoma, an international multidisciplinary classification was sponsored by the International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society. This new adenocarcinoma classification is needed to provide uniform terminology and diagnostic criteria, especially for bronchioloalveolar carcinoma (BAC), the overall approach to small nonresection cancer specimens, and for multidisciplinary strategic management of tissue for molecular and immunohistochemical studies. Methods: An international core panel of experts representing all three societies was formed with oncologists/pulmonologists, pathologists, radiologists, molecular biologists, and thoracic surgeons. A systematic review was performed under the guidance of the American Thoracic Society Documents Development and Implementation Committee. The search strategy identified 11,368 citations of which 312 articles met specified eligibility criteria and were retrieved for full text review. A series of meetings were held to discuss the development of the new classification, to develop the recommendations, and to write the current document. Recommendations for key questions were graded by strength and quality of the evidence according to the Grades of Recommendation, Assessment, Development, and Evaluation approach. Results: The classification addresses both resection specimens, and small biopsies and cytology. The terms BAC and mixed subtype adenocarcinoma are no longer used. For resection specimens, new concepts are introduced such as adenocarcinoma in situ (AIS) and minimally invasive adenocarcinoma (MIA) for small solitary adenocarcinomas with either pure lepidic growth (AIS) or predominant lepidic growth with ≤5 mm invasion (MIA) to define patients who, if they undergo complete resection, will have 100% or near 100% disease-specific survival, respectively. AIS and MIA are usually nonmucinous but rarely may be mucinous. Invasive adenocarcinomas are classified by predominant pattern after using comprehensive histologic subtyping with lepidic (formerly most mixed subtype tumors with nonmucinous BAC), acinar, papillary, and solid patterns; micropapillary is added as a new histologic subtype. Variants include invasive mucinous adenocarcinoma (formerly mucinous BAC), colloid, fetal, and enteric adenocarcinoma. This classification provides guidance for small biopsies and cytology specimens, as approximately 70% of lung cancers are diagnosed in such samples. Non-small cell lung carcinomas (NSCLCs), in patients with advanced-stage disease, are to be classified into more specific types such as adenocarcinoma or squamous cell carcinoma, whenever possible for several reasons: (1) adenocarcinoma or NSCLC not otherwise specified should be tested for epidermal growth factor receptor (EGFR) mutations as the presence of these mutations is predictive of responsiveness to EGFR tyrosine kinase inhibitors, (2) adenocarcinoma histology is a strong predictor for improved outcome with pemetrexed therapy compared with squamous cell carcinoma, and (3) potential life-threatening hemorrhage may occur in patients with squamous cell carcinoma who receive bevacizumab. If the tumor cannot be classified based on light microscopy alone, special studies such as immunohistochemistry and/or mucin stains should be applied to classify the tumor further. Use of the term NSCLC not otherwise specified should be minimized. Conclusions: This new classification strategy is based on a multidisciplinary approach to diagnosis of lung adenocarcinoma that incorporates clinical, molecular, radiologic, and surgical issues, but it is primarily based on histology. This classification is intended to support clinical practice, and research investigation and clinical trials. As EGFR mutation is a validated predictive marker for response and progression-free survival with EGFR tyrosine kinase inhibitors in advanced lung adenocarcinoma, we recommend that patients with advanced adenocarcinomas be tested for EGFR mutation. This has implications for strategic management of tissue, particularly for small biopsies and cytology samples, to maximize high-quality tissue available for molecular studies. Potential impact for tumor, node, and metastasis staging include adjustment of the size T factor according to only the invasive component (1) pathologically in invasive tumors with lepidic areas or (2) radiologically by measuring the solid component of part-solid nodules.