Background The pathogenesis of infantile haemangioma (IH) is unknown. Several mechanisms have been proposed, including hypoxia, which triggers upregulation and stabilization of hypoxia-inducible factor (HIF)1. HIF1 stimulates downstream transcription of target genes that enhance angiogenesis. AimTo identify possible involvement of hypoxia in the pathogenesis of IH, as hypoxia signalling constitutes a potential therapeutic target. MethodsIH tissue samples collected during the period 1991-2011 (preserved in paraffin wax) were immunohistochemically analysed for HIF1 and the known HIF1 targets: BCL2/adenovirus E1B kD-interacting protein family member 3 (BNIP3), carbon anhydrase (CA)-IX, glucose transporter (GLUT)-1, phosphorylated protein kinase B (pAKT), phosphorylated S6 protein (pS6) and vascular endothelial growth factor (VEGF). Four observers independently assessed the findings. ResultsOf the 10 IH samples, 2 appeared to be in the growth phase. In all samples, GLUT-1, BNIP3, pAKT and VEGF were positive, CA-IX was weakly positive, and HIF1 was negative. pS6 was positive in 9/10 cases and negative in 1/10. ConclusionsSeveral factors implicated in hypoxia-induced angiogenesis may be involved in IH development. However, the small sample size and retrospective approach of the study preclude definitive conclusions. Prospective studies are needed to conclusively determine which of the factors involved in the (hypoxia) cascade are required for an IH to grow, and could thus be a possible target of drugs for IH treatment.