EPAS1 and neoplasm: Hypoxic tumour signature is usually monitored by the levels of hypoxia-inducible factor 1α or 2α (HIF-1α or HIF-2α) or by the expression of their target genes (for example, carbonic anhydrase IX (CA9)).15 While the correlation between a hypoxic signature and poor clinical prognosis is accepted for several tumours, including NB,6, 16, 17 the duration and levels of hypoxia responsible for this association remain unknown.