EPAS1 and neuroblastoma: Serial sections were prepared and the spatial distribution of NESP55 immunoreactive cells was studied in relation to the vascular stroma and to expression of markers for hypoxia and phenotype: nuclear HIF2α immunoreactivity was selected as an operational definition of a cellular response to hypoxia and expression of VEGFA and of IGF2 were used as independent hypoxia markers, previously validated in neuroblastoma [11], [12], [41].