We measured the number of circulating endothelial progenitor cells (CD31+CD34+CD133+CD45dim) by four-color flow cytometry using blood samples from 57 patients with breast cancer who received neoadjuvant chemotherapy (5-fluorouracil + epirubicin + cyclophosphamide (FEC), docetaxel + cyclophosphamide (TC), cisplatin + docetaxel (TP)). This evidence concerns the gene PECAM1 and breast cancer.