[New TNM classification of malignant lung tumors 2009 from a pathology perspective]

Based on the IASLC multicenter data collected worldwide on 81495 patients diagnosed or registered with lung cancer between 1990 and 2000, the T, N, and M descriptors were analyzed and recommendations for changes in the seventh edition of the TNM classification were proposed on the basis of differences in survival. This new TNM classification replaces the old UICC classification and the staging system according to C. Mountain 1997. The changes principally affect the T and M classifications. For the T component, tumor size was found to have prognostic relevance and its analysis led to recommendations to subclassify T1 into T1a and T1b, and T2 tumors into T2a and T2b and to reclassify T2 tumor>7 cm into T3 tumors. In the M category, M1 was recommended to be subclassified into M1a (contralateral lung nodules and pleural dissemination) and M1b (distant metastasis). There is no change in the N category. The proposed changes for the new stage grouping are to upstage T2b N0 M0 from stage IB to stage IIA and to downstage T2a N1 M0 from stage IIB to stage IIA and T4 N0-N1 M0 from stage IIIB to stage IIIA. The particulars of the new classification are discussed in the context of practice-relevant aspects from a pathology perspective view.