PECAM1 and neoplasm: EO771 tumours were also significantly more hypoxic (p = 0.0063) and had a higher CD31+ vessel density (p = 0.0005) than B16-F10 tumours (Fig 6B and 6C), while the number of perfused vessels per field were similar in EO771 compared with B16-F10 tumours (Fig 6D).