PECAM1 and neoplasm: Immunohistochemistry of CD31 showed that the number of microvessels around tumor hypoxic areas was higher in the eribulin-treated groups than in the control group: 1.1-fold (12.1 ± 6.3 vessels/mm2) and 1.6-fold (18.0 ± 6.4 vessels/mm2) of the control value (11.0 ± 1.2 vessels/mm2), respectively, for 0.3 and 1.0 mg/kg eribulin treatments (Fig. 4).