PECAM1 and neoplasm: Immunohistochemical analysis demonstrated faint expression of CD68 and CD31 (Fig. 2A, B) in a fraction of tumour cells (approximately 70% and 30% of all tumour cells, respectively); smooth muscle actin (SMA) was positive only in isolated cells; CD21, CD23, CD45 (LCA), CD34, ERG, factor VIII, podoplanin (D2-40), S100, desmin, calponin, h-caldesmon, ALK and CD1a were consistently negative.