Angiogenesis, the formation of new blood vessels from the endothelium, develops in response to metabolic demands of tissues and tumors, and is thought to play an essential role in progression of solid tumors, including lung cancer (1) . It is observed in early stages of lung carcinogenesis, such as bronchial dysplasia and carcinomain situ, which display increased vascularity when compared with normal bronchial epithelium and hyperplasia (2) . In addition, several reports have shown that microvascular density in primary tumors confers a poor prognosis in early-stage non-small cell lung cancer (NSCLC) (3 ,4) .
