PECAM1 and hemangioma: To learn if SOX18 is involved, we first explored the expression of SOX18 in vivo in hemangioma tissue sections from three patients and in vitro in different cell populations derived from infantile hemangiomas: SOX18 protein was observed in a sup-population of CD31-positive endothelial cells (Figure 3A, arrows) and SOX18 mRNA was expressed in ECFC (positive control) and in HemEC, whereas HemSC showed low expression and hemangioma pericytes were completely devoid of SOX18 transcripts (Figure 3—figure supplement 1).