The 8^th TNM edition for lung cancer: a critical analysis

The 8^th edition of the tumor, node and metastasis (TNM) classification provides several new categories and for the first time, some prospective data are included. The T (tumor) descriptor is further subdivided with 1 cm increments for T1 and T2 disease. For metastatic disease (M descriptor) the new M1b category comprises patients with only one metastasis in one distant organ, whereas M1c implies multiple distant metastases in one or several organs. There are no changes regarding the nodal map and N component but new categories are suggested for further analysis, subdividing the N1 and N2 descriptors into involvement of single or multiple lymph node stations. The residual tumor (R) classification, related to completeness of resection, was revised in the 7^th edition specifically for lung cancer resection and has been maintained in its revised form in the 8th edition. For the first time, a thorough analysis has been made of patients with multiple lung lesions distinguishing four distinct categories. Although prospective data were used for this edition, their overall number is low and more good-quality prospective data collection coming from all continents is certainly required. Main challenge for subsequent editions is the combination of specific anatomical factors with detailed immunohistochemical data and information from biomarkers and mutational changes inside the primary tumor as well as those occurring in lymph node and distant metastases. In this way not only prognosis of our patients with lung cancer will be better determined, but more specific diagnostic and therapeutic algorithms may be applied.