[Introduction to the 9^th edition of TNM classification for lung cancer]

Lung cancer is the second commonly diagnosed cancer and remained the leading cause of cancer-related death, with an estimated 1.8 million deaths in 2020. The identification of driver gene mutation and administration of corresponding tyrosine kinase inhibitor have improved overall survival and quality of life in advanced lung cancer patients. Check point inhibitor has revolutionized treatment strategy of driver gene negative advanced NSCLC patients. TNM staging system is the most widely used classification method, providing an international common language during academic communication and important tool for predicting prognosis and subsequent treatment decision making. Accumulating knowledge about prognostic factors in lung cancer promotes the update of TNM classification. In the World Conference on Lung Cancer (WCLC) held in Singapore, September, 2023, International Association for Study of Lung Cancer (IASLC) released the forthcoming 9^th edition of TNM classification for lung cancer, which is supposed to be adopted at January, 2024. The manuscript discussed the history, data resource and limitation of the TNM staging system.