There is a growing rationale for analysing somatic events in PCC and PGL tumours as a diagnostic test: (1) EPAS1 mutations may occur early in embryogenesis and these mosaic carriers are not found by analysis of DNA in peripheral blood [16], [46]; (2) Translational studies have suggested using genotype as predictive markers for sensitivity to targeted therapy; SDHx/VHL mutations might benefit from antiangiogenic treatment whereas RET/NF1/TMEM127/MAX driven tumours could benefit from inhibitions of kinase pathways [47], [48]. The gene discussed is EPAS1; the disease is neoplasm.