Version July 2025
INTRODUCTION —
The tumor, node, metastasis (TNM) staging system for lung cancer is an internationally accepted system used to characterize the observable extent of disease. The TNM system combines features of the tumor into stage groups that correlate with prognosis and are often linked to treatment recommendations. The design criteria for stage classifications balance individual tumor characteristics as well as external priorities for applicability and implementation across international health systems. Specifically, criteria for stage classification include applicability across a broad spectrum of patients and geographic regions.
This topic discusses the TNM staging system for lung cancer. The purpose of TNM staging is to provide a description of the anatomic extent of cancer that can be communicated to others, assist in treatment decisions, and indicate prognosis. Consistent application of staging criteria permits valid comparisons of patient cohorts, particularly in regards to the outcomes associated with different therapeutic options. In clinical practice, the links between stage, treatment, and prognosis are complex. For any individual patient, TNM stage should be combined with the unique clinical and socioeconomic characteristics of the patient, the molecular features of the tumor, and treatment selections to guide the most accurate prognostic assessments.
The ninth edition of the TNM staging system and the evidence supporting it are described in this topic (table 1). The ninth edition was effective internationally as of January 1, 2025 [1]. The clinical manifestations, diagnosis, pathology, and management of lung cancer are discussed in other topics.
●(See "Clinical manifestations of lung cancer".)
●(See "Overview of the initial evaluation, diagnosis, and staging of patients with suspected lung cancer".)
●(See "Overview of the initial treatment and prognosis of lung cancer".)
●(See "Management of stage I and stage II non-small cell lung cancer".)
●(See "Systemic therapy in resectable non-small cell lung cancer".)
●(See "Management of stage III non-small cell lung cancer".)
●(See "Overview of the initial treatment of advanced non-small cell lung cancer".)
●(See "Limited-stage small cell lung cancer: Initial management".)
●(See "Extensive-stage small cell lung cancer: Initial management".)
●(See "Treatment of refractory and relapsed small cell lung cancer".)
●(See "Large cell neuroendocrine carcinoma of the lung".)
●(See "Pathology of lung malignancies".)
PATHOLOGIC, CLINICAL, AND OTHER STAGING DISTINCTIONS —
Different staging systems are used prior to and after surgical resection, as described below.
●Clinical-diagnostic staging – Clinical-diagnostic staging (cTNM) is based on imaging findings with or without additional information from minimally invasive biopsy procedures, such as endobronchial ultrasound-guided biopsy.
●Surgical-pathologic staging – TNM staging is described as surgical pathologic (pTNM) when it is based on findings combined from surgical resection or exploration of the primary tumor and lymph nodes with additional information from clinical imaging studies.
The individual definitions of the T, N and M categories are the same whether assessed clinically or pathologically (table 1). The same TNM groupings are used to determine the clinical-diagnostic stage and surgical-pathologic stage, as well as retreatment stage and autopsy stage. The suffix "X" is attached (ie, TX, NX) if the extent of disease cannot be assessed for any of these features.
NSCLC VERSUS SCLC AND OTHER NEUROENDOCRINE CANCERS —
Lung cancer is clinically subclassified into two major categories based on a combination of clinical and pathologic features: non-small cell lung cancer (NSCLC) and small cell lung carcinoma (SCLC). NSCLC including the subtypes adenocarcinoma and squamous cell carcinoma is the most common tumor group by incidence rates. In practice, TNM staging is routinely applied to NSCLC without modification or clinical reclassifications.
SCLC comprises approximately 15 percent of all lung cancers. SCLC is a neuroendocrine carcinoma that has overlapping pathologic features with other rare tumors including large cell neuroendocrine carcinoma of the lung, as well as typical and atypical carcinoid tumors. Neuroendocrine tumors have distinctly different molecular, pathologic, and clinical features as well as treatment approaches when compared with NSCLC types. The utility of the staging system for SCLC and neuroendocrine tumors is complemented by additional classification in clinical treatment groups.
SCLC has been routinely approached using a two-stage classification system of clinical-limited or clinical-extensive disease. The origin of this approach is a historical classification scheme developed in part by the Veterans Administration Lung Study Group (VALSG) decades ago, which has been updated and internationally adopted [2]. The utility of this two-stage system is the simplicity of stage groupings by whether or not the tumor and regional nodes can be adequately covered in an effective radiation field. Although the TNM system derivation and validation cohorts included relatively few early-stage SCLC cases, the TNM system is highly applicable to SCLC and provides more precision in classifying the disease than the two-stage system. To facilitate ongoing practical clinical care and to support ongoing development of registries and standardized clinical trials, a combined approach for staging SCLC using both the TNM staging system and the VALSG categories is recommended. (See "Pathobiology and staging of small cell carcinoma of the lung", section on 'Staging'.)
Similarly, rare neuroendocrine tumors including typical and atypical carcinoid tumors may be staged using the TNM classification system for lung cancer. In a cohort of 205 carcinoid tumors, the TNM system was predictive of survival and maintained clinical utility. However, in addition to the TNM factors of tumor size and nodal stage, the histology of the tumor (typical versus atypical) was also found to be highly predictive of recurrence and this factor should be considered in the initial assessment of pulmonary carcinoid tumors [3]. Additional factors particularly relevant to the management of lung carcinoid tumors include the feasibility of surgical resection based primarily on whether they arise proximally and involve large airways or are peripheral and surrounded by normal lung parenchyma. (See "Lung neuroendocrine (carcinoid) tumors: Treatment and prognosis".)
NINTH EDITION OF THE TNM SYSTEM
Changes between current and prior staging systems — Following publication of the eighth edition of the TNM, the International Association for the Study of Lung Cancer (IASLC) collected further lung cancer cases diagnosed between 2011 and 2019 to further refine lung cancer staging and establish the ninth edition of the staging system (table 1). The survival by clinical stage is indicated in the figure (figure 1).
Key changes between the eighth (table 2) and the ninth editions (table 1) of the TNM staging system include the following [1]:
Changes to primary tumor (T) staging
●Invasion of adjacent lobe has been added as a T2a category.
●Azygos vein, thoracic nerve roots, and stellate ganglion involvement are added as a T3 category.
●Thymus, vagus nerve, supra-aortic arteries, brachiocephalic veins, subclavian vessels, vertebral body, lamina, spinal canal, cervical nerve roots, brachial plexus (ie, trunks, divisions, cords, or terminal nerves) involvement are specified as T4 category criteria.
Changes to regional lymph node (N) staging
●A new subclassification of N2 disease depending on single-station or subcarinal nodal involvement (N2a) versus multiple station involvement, with or without subcarinal involvement (N2b).
The rationale for this change was a worsened overall survival for those with clinical N2b versus N2a disease (five-year estimate 31 versus 42 percent, respectively, HR 1.27), as well as pathologic N2b versus N2a disease (five-year estimate 40 versus 51 percent, HR 1.46), in analysis of the IASLC database.
Changes to distant metastasis (M) staging
●M1c subdivided into M1c1 (multiple extrathoracic metastases in a single organ system) and M1c2 (multiple extrathoracic metastases in multiple organ systems).
The rationale for the changes was that patients with M1c2 disease had worse survival than patients with M1c1 disease.
Changes to prognostic stage groups — Changes in prognostic staging groups are as follows and summarized in the figure (figure 2):
●T1 N1 M0 changed to stage IIA (previously stage IIB disease).
●T1 N2a M0 assigned to stage IIB (T1 N2 M0 was previously stage IIIA disease).
●T2 N2b M0 assigned to stage IIIB (T2 N2 M0 was previously stage IIIA disease).
●T3 N2a M0 assigned to stage IIIA (T3 N2 M0 was previously stage IIIB disease).
Additional factors
●The addition of spread through air spaces (STAS) as a histologic descriptor was based on its association with worse overall and recurrence-free survival, as well as higher risks of local and distant recurrence.
INFORMATION FOR PATIENTS —
UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Beyond the Basics topics (see "Patient education: Lung cancer risks, symptoms, and diagnosis (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Introduction
•The tumor, node, metastasis (TNM) staging system for lung cancer is an internationally accepted system used to characterize the observable extent of disease. The purpose of TNM staging is to provide a description of the extent of cancer that can be easily communicated to others, assist in treatment decisions, and serve as a prognostic indicator. (See 'Introduction' above.)
•The TNM staging system relies on anatomic, macroscopic groupings of disease with similar prognoses rather than on molecular characterization.
●Ninth edition of the TNM system
•The TNM staging system predicts survival, but should not be used alone to dictate treatment. Patient-specific factors and health system resources must be considered. (See 'Ninth edition of the TNM system' above.)
•The most recent version of the TNM staging system is the ninth edition of the "TNM Classification of Malignant Tumors," effective internationally as of January 1, 2025. The ninth edition preserved the majority of features in the prior systems, but refined and subclassified tumor stage groupings, as well as T and M descriptors (table 1).
