VHL and adrenal gland pheochromocytoma: Unsupervised cluster analysis of genome-wide expression performed on hereditary PCC has revealed two dominant groups associated with kinase receptor signals, which have been linked to NF1 and RET mutants (the first cluster) and hypoxia and angiogenesis through stabilization of hypoxia-inducible factor alpha (the second cluster), which occurs in all VHL- and SDHx-mutant tumors [12, 30, 34].