PECAM1 and neoplasm: Additionally, in some vessels, parts of the endothelial cell outline were not reactive to CD31, maybe constituting a vessel wall mosaicism, where both endothelial and tumor cells line the blood vessel (Figure 1B), or could correspond to an angiomatoid pattern, with vessels only covered by round or polygonal cells, which could be neuroblastic cells, immune cells or stem cells (Figure 1C).