Evolution of the N Descriptor Classification within the Pulmonary Cancer TNM Staging System

Abstract

Introduction: The nodal classification of lung cancer has remained unchanged since the 4^th edition of the tumor-node- metastasis staging system (TNM).

Objective: To analyze the nodal classification from the beginning of the TNM classification to the present for lung localization.

Methods: A search was performed in the Scopus, Medline, Cochrane, Hinari and Redalyc databases, using the descriptors TNM, número de ganglios [number of nodes], relación entre glanglios [relationship between nodes], pronóstico [prognosis]. The searches were specifically in Spanish and English, with the following keywords: neoplasias pulmonares [lung neoplasms], estadificación de neoplasias [staging of neoplasms], escisión de ganglio linfático [lymph node excision], metástasis linfática [lymphatic metastasis], índice ganglionar [nodal index], procedimientos quirúrgicos pulmonares [pulmonary surgical procedures].

Results: No changes were made in two latest classifications, although databases were analyzed that included, in the clinical and pathological classification, the number of lymph node stations affected; however, these did not show a clear separation between each of the individual subcategories in a consistent manner, particularly for N1 nodes and skip metastases. Notwithstanding, in the analysis of the N2 subcategories, clinical and statistical significance was observed in terms of prognosis, which allowed changing the N classification, as well as including it in the 9^th edition of the TNM.

Conclusions: The creation of prognostic groups, according to the location in stations and zones, as well as the number of affected nodes and the relationships between them, is a factor to be taken into account in the new editions of the TNM.