The eighth TNM classification for malignant pleural mesothelioma

In 1994, the first widely accepted tumor, node and metastasis (TNM) classification for malignant pleural mesothelioma (MPM) was published by the International Mesothelioma Interest Group (IMIG) (1). This was the result of a consensus meeting in June 1994 during the Seventh World Conference of the International Association for the Study of Lung Cancer (IASLC). Before this staging system, diagnosing and accurately staging MPM was a challenging task as clear guidelines or a universally accepted classification for staging MPM did not yet exist. This was the first MPM staging system that was based on outcomes of several retrospective series and clinical trials. This TNM classification was then also adopted and revised by the American Joint Commission on Cancer (AJCC) and the Union for International Cancer Control (UICC) leading to the previously used seventh edition of the classification (2-4). However, over the years more and more limitations of this staging system became apparent. First of all, the data used for establishing the classification was mainly derived from small single institution retrospective series (5). Furthermore, translating clinical and pathological findings into a corresponding TNM stage sometimes proved quite difficult. To address these matters, in 2016 the IASLC published a number of recommendations for the eighth TNM classification for MPM based on analysis of recent large retrospective series and clinical trials. With regards to the previous edition, a number of important revisions have been made in the different descriptors (6-8)