RRAS and neoplasm: Despite the fact that WT skin had significantly less blood vessels than the R-Ras KO mice after the DMBA/TPA-treatment, the tumour formation required vascular supply in the WT mice as evidenced by the increased number of blood vessels beneath the small and large tumours, the highest vascular density being beneath the large >2 mm tumours (P < 0.0001 non-tumour epidermis vs. large tumours and P = 0.0036 small vs. large tumours, Fig. 3b).