Quantification of EPC EPCs will be quantified as cells showing dual positivity for the cell surface / transmembrane markers: Cluster of Differentiation 24 (CD24) and Kinase Domain Receptor (KDR). Standardized flow cytometry protocols will be employed. In brief, the cells will be thawed and immunofluorescent cell staining will be performed using the fluorescent conjugated antibodies: CD34-fluorescein isothiocyanate (FITC) and KDR-phycoerythrin (PE). For each patient, a corresponding negative control with IgG2a-FITC-PE will be processed. The number of circulating EPCs will be expressed in terms of the total number of cells displaying dual positivity for CD24 and KDR per µl blood originally processed.