PECAM1 and neoplasm: For CD31 staining, there was a significant difference in endothelial cell count within the tumor bed (p < 0.05) between groups, with responders showing a lower mean cell count (cells/field = 3.5 ± 1.8) in contrast to non-responders (cells/field = 9.6 ± 4.3) [Figure 7B, 7C].