PECAM1 and myelodysplastic syndrome: n = 163 cells (total 0.7%, 0.5% in HY, and 0.7% in MDS) were classified as ECs by expression of key markers such as Fatty Acid Binding Protein 4(FABP4), von Willebrand factor, and Platelet And Endothelial Cell Adhesion Molecule 1(PECAM1) (supplemental Table 6).