Significance of the presence of microscopic vascular invasion after complete resection of Stage I-II pT1-T2N0 non-small cell lung cancer and its relation with T-Size categories: did the 2009 7th edition of the TNM staging system miss something?

Introduction: The aim of this study was to assess the significance of microscopic vascular invasion (MVI) in a population of resected patients with early-stage non-small cell lung cancer (NSCLC), along with an analysis of the effect of the combination of MVI and tumor size for the T-size categories T1a-T2b according to the 2009 7th edition of the tumor, node, metastasis (TNM) classification. Methods: From January 1993 to August 2008, 746 patients with pT1-T2N0 NSCLC received resection at our institution. MVI was ascertained using histopathological and immunohistochemical techniques. Results: MVI was observed in 257 patients (34%). Prevalence was higher in adenocarcinoma (ADK) than in squamous cell carcinoma (p = 0.002). A significant correlation was found between MVI and ADK (p = 0.03), increased tumor dimension (p = 0.05), and the presence of tumor-infiltrating lymphocytes (p = 0.02). The presence of MVI was associated with a reduced 5-year survival overall (p = 0.003) and in ADK (p = 0.0002). In a multivariate survival analysis, MVI was an indicator of poor survival overall (p = 0.003) and in ADK (p = 0.0005). In each T category (T1a-T2b) of the 2009 TNM staging system, survival of MVI+ patients was significantly lower than the corresponding MVI-patients; T1a and T1b MVI+ patients had a survival similar to MVI-T2 patients. Conclusions: The finding of MVI in pT1-T2N0 NSCLC is frequent. MVI correlates with adenocarcinoma histotype, increased tumor dimensions, and tumor-infiltrating lymphocytes. The presence of MVI is an independent negative prognostic factor. In our experience, MVI was a stronger prognostic indicator than T size in T1a-T2b categories according to the 2009 TNM staging system.