# TNM 9: what changed in lung cancer staging

Source: https://onco.cc/terms/tnm-9-lung-cancer/  
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## TL;DR

Lung cancer has been staged by the ninth edition of TNM since 1 January 2025. The T categories are unchanged; N2 was split into N2a and N2b by how many mediastinal node stations are involved, M1c was split by how many organ systems carry metastases, and several stage groups moved as a result.

## Summary

The International Association for the Study of Lung Cancer revises the lung TNM classification roughly every eight years from a purpose-built international database; for the ninth edition it collected 124,581 patients diagnosed between 2011 and 2019 and analysed 76,518 of them. The T subcommittee tested the eighth-edition descriptors and recommended no change, so T is identical between the two editions. N changed: N2 is subdivided into N2a, involvement of a single ipsilateral mediastinal or subcarinal station, and N2b, involvement of multiple ipsilateral mediastinal stations with or without the subcarinal station. M changed at the far end: M1a and M1b are validated unchanged, while M1c is subdivided into M1c1, several metastases within one extrathoracic organ system, and M1c2, several metastases across organ systems, both remaining in stage group IVB. The stage groups were rebuilt to follow the new N and M categories: T1N1 moves to IIA, T1N2a to IIB, T3N2a to IIIA, and T2aN2b and T2bN2b to IIIB. The edition came into force on 1 January 2025. Two practical consequences: a systematic nodal staging that records which stations are involved, rather than a single positive sample, is now needed to assign N; and survival series that span the change cannot be pooled without restaging, because the same disease carries different labels either side of it. NICE NG122 still states that its recommendations were developed with the 7th edition of the AJCC staging system.

## Fields

- Kind: Term
- Last checked: 2026-09-25
- Also known as: TNM 9; ninth edition TNM; TNM ninth edition lung; 9th edition TNM lung cancer; N2a; N2b; M1c1; M1c2
- Tags: lung

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/TNM_staging_system
- Br J Radiol 2025: something old something new, introduction to the ninth edition TNM classification of lung cancer (effective 1 January 2025): https://doi.org/10.1093/bjr/tqaf161
- Rami-Porta, J Thorac Oncol 2024: IASLC lung cancer staging project, proposals for revision of the TNM stage groups in the forthcoming ninth edition (76,518 patients analysed of 124,581 registered): https://doi.org/10.1016/j.jtho.2024.02.011
- J Thorac Oncol 2024: IASLC lung cancer staging project, proposals for the revisions of the T descriptors in the forthcoming ninth edition (no change recommended): https://doi.org/10.1016/j.jtho.2023.12.006
- J Thorac Oncol 2024: IASLC staging project for lung cancer, proposals for the revision of the M descriptors in the forthcoming ninth edition (M1c split into M1c1 and M1c2): https://doi.org/10.1016/j.jtho.2024.01.019
- J Thorac Oncol 2023: IASLC lung cancer staging project, the new database to inform revisions in the ninth edition of the TNM classification: https://doi.org/10.1016/j.jtho.2023.01.088
- Int J Cancer 2026: the 9th edition of the UICC TNM classification of malignant tumours, updates and rationale for change: https://doi.org/10.1002/ijc.70561
- NICE NG122: lung cancer, diagnosis and staging (published 28 March 2019, last updated 8 March 2024): https://www.nice.org.uk/guidance/ng122/chapter/Diagnosis-and-staging

## Connected records

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- terms: [Disease-specific staging and risk systems (FIGO, Ann Arbor, IPI, R-ISS, ELN, IMDC)](https://onco.cc/terms/staging-systems/), [Endobronchial ultrasound (EBUS-TBNA)](https://onco.cc/terms/ebus-tbna/), [Malignant pleural effusion](https://onco.cc/terms/malignant-pleural-effusion/), [Mediastinal lymph node stations](https://onco.cc/terms/mediastinal-lymph-node-stations/), [Oligometastatic disease](https://onco.cc/terms/oligometastatic/), [Pancoast (superior sulcus) tumour](https://onco.cc/terms/pancoast-tumour/), [Resectability in lung cancer](https://onco.cc/terms/resectability-lung-cancer/), [Spread through air spaces (STAS)](https://onco.cc/terms/spread-through-air-spaces/), [Sublobar resection (segmentectomy and wedge)](https://onco.cc/terms/sublobar-resection/), [TNM staging](https://onco.cc/terms/tnm-staging/)

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