Usuda et al. showed in their research that VEGF expression is significantly higher in adenocarcinoma compared to squamous cell carcinomas, and that VEGF can be a positive regulator of pericytes and angiogenesis, thus affecting the proliferation of endothelial cells and maturation of blood vessels of tumor, which could result in a favorable outcome in well-differentiated lung cancer [39]. This evidence concerns the gene VEGFA and squamous cell carcinoma.