Staging of non-small-cell lung cancer (NSCLC) is currently evolving. The conventional TNM system was first proposed in 1946 by Denoix and is an anatomically structured system . It provides information about the size and local extension of the primary tumor (T stage), the regional lymph node metastasis (N stage), and distant hematogenous cancer spread (M stage). The TNM staging system also groups tumors of various TNM stage into subgroups I, II, III, and IV. Such division not only provides prognostic information, but also directs therapeutic decisions for tumors of different grouping categories. TNM staging was adapted by the American Joint committee for Cancer Staging (AJCC) in 1974 , and has been through further revisions in 1986  and 1997 . The staging is based on clinical information including physical examination findings, endoscopic examination findings, histologic examination of biopsy specimens, and imaging information from computed tomography (CT) scans, magnetic resonance imaging (MRI) scans, bone scans, and in the recent years, positron emission tomography (PET) scans.
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