Unique intravascular tumor microenvironment predicting recurrence of lung squamous cell carcinoma.

Purpose: Histological vascular invasion (VI) by tumors is a risk factor for recurrence after surgical resection. However, VI features vary histologically. The aim of this study was to identify characteristic VI features that are associated with recurrence in squamous cell carcinoma (SCC) of the lung.

Methods: We enrolled 149 patients with pathological stage I primary lung SCC in this study and examined whether the presence, frequency, and size of VI were associated with recurrence. We also evaluated immunophenotypes of carcinoma cells and stromal cells within VI areas.

Results: Of the 149 patients, 58 had tumors with VI. The presence of VI was significantly correlated with shorter recurrence-free survival (RFS) (P = 0.018). Although VI frequency was not associated with RFS, larger VI size (>425 µm) was significantly correlated with shorter RFS (P = 0.003). Carcinoma cells within larger VI areas expressed significantly higher levels of podoplanin, cancer stem cell marker (P = 0.039); higher numbers of CD34(+) microvessels (P = 0.009), CD204(+) macrophages (P = 0.026), and α-SMA(+) myofibroblasts (P = 0.056) were present within larger VI areas than within smaller VI ones.

Conclusions: Our results indicate that larger VI areas are a predictor for recurrence in lung SCC; also, within the larger blood vessel, cancer stem cells and abundant stromal cells can create a more favorable microenvironment for tumor metastasis.