PECAM1 and neoplasm: These vascular alterations―known as “vascular regression”―are characterized by progressive disengagement of endothelial cells from surrounding supportive structures in the absence of angiogenic stimulation.29, 30, 31 This phenomenon is primarily led by Ang‐2, which induces endothelial cell apoptosis and detachment of endothelial cells from surrounding pericytes.24, 25, 30, 31 Our histologic study also showed relatively low expression of CD31, VEGFR2, and NG2 in the tumor center in comparison with tumor periphery.