PECAM1 and vascular neoplasm: Immunohistochemically, the epitheloid cells showed a strongly increased proliferation (Ki-67 90%) with a strong expression of erythroblast-transformation-specific-related gene (ERG), platelet endothelial cell adhesion molecule (CD31), cytokeratin AE1/AE3, and, only sporadically, CD34, leading to the diagnosis of a highly proliferative vascular tumor (Fig. 4).