Molecular subgroups characterized by activation of the Sonic Hedgehog ([[SHH]]) and Wingless (WNT) pathways are common to all studies generating these data. [[Non-SHH]]/[[WNT]] subgroups number between two and four, are less readily separated on principal components analysis, and are not obviously associated with abnormalities of any cell signaling pathway. While less is known about non-SHH/WNT tumors, evidence suggests that at least one subgroup may be driven by amplification and/or overexpression of MYC