To investigate whether CD34 expression contributes to the cancer-initiating status of the α6-integrin-positive cells in UV-induced skin tumours, cells from SCC tumours were stained with PI to exclude the dead cells, lymphocytes (CD11b+), immune cells (CD45+) and endothelial cells (CD31+) in the tumour cell population. This evidence concerns the gene PECAM1 and neoplasm.