PECAM1 and neoplasm: Accordingly, we performed chromogenic in situ hybridization (CISH) for MDM2 and immuno-fluorescence in situ hybridization (immuno-FISH) for (1) CD31 (a marker of vascular endothelial cells) and MDM2, and (2) aSMA and MDM2, to address whether immunohistochemically confirmed endothelial (CD31-positive) cells and smooth muscle (aSMA-positive) cells exhibit MDM2 amplification, the gold standard to demonstrate the presence of DDLPS tumor cells [1]; CD31, instead of ERG, was used for these analyses because ERG is a nuclear protein and masks the signals of ISH.