Introduction: Although invasion of the visceral pleura (VPI) by non-small cell lung cancer (NSCLC) is a TNM-relevant diagnostic criterion and is known to affect the patients' prognoses, until recently there were no standardized or internationally accepted guidelines. This resulted in a diagnostic ambiguity leading to different tumor staging systems and to hardly comparable patient collectives in research studies world wide. The major problem in this issue is to exactly define what constitutes for the diagnosis of VPI with respect to anatomical landmarks.
Methods: In order to address this problem we investigated the pleural infiltration depth of 173 NSCLC specimens without lymph node metastases and proven tumor-related death using elastic stains and a scoring system referring to prominent pleural elastic layers, the lamina elastica externa and interna, as anatomical landmarks.
Results: Performing comparative Kaplan-Meier survival analyses for each patient collective we could not find any significant difference in the patients' survival. This indicates that a differential evaluation of the tumor infiltration depth according to the elastic layers is not practicable.
Conclusions: Our findings support the consequent application of the recently proposed, pragmatic approach of the international staging committee for lung cancer (IASLC) to define an internationally accepted and standardized staging system for VPI.