[Guide to the application of the 9th TNM classification for lung cancer : Statement/position paper of the Thoracic...

The 9th TNM Classification for Lung Cancer, based on IASLC data, was published in January 2025. This edition is currently available online as a download or printed manual in English ( www.iaslc.org/research-education/publications-resources-guidelines/staging-manual-thoracic-oncology-3rd-edition ). Key changes include the subclassification of pN2 into pN2a/b and M1c into M1c1/2, leading to improved prognostic differentiation and reclassification of individual TN combinations into UICC stages. The T-category remains formally unchanged but has been anatomically refined. A survey of 18 pathology institutes conducted by the Thoracic Pathology Working Group revealed that 83% use TNM 8 and only 22% already use TNM 9; 39% subclassify pN2 and 67% document pleural status (PL0-3). The Thoracic Pathology Working Group recommends immediate structured implementation of TNM 9, in particular the N2 subclassification, as well as dual documentation of TNM 8 and 9 during the transition phase until January 2026. Formal implementation in clinical practice is planned for this date. R0(un) should be commented on optionally, and the pleural status should be specified in detail (PL0-3).