PECAM1 and skin basal cell carcinoma: Figure 2 shows samples of CD31 and CD105 immunostaining in BCC and SCC. There was a strong correlation between CD31 and CD105 Chalkley score (Pearson's R = 0.8; P < 0.001). We next proceeded to evaluate the degree of proliferating endothelium by dividing the CD105-Chalkley score by the CD31-Chalkley score. The mean CD105/CD31 quotient was 0.96 for BCC (SD = 0.16) and 0.79 for SCC (SD = 0.16) (P = 0.024).