IDH1 and glioma: Given that both canonical and non-canonical IDH1 mutations likely represent early clonal mutations that may even precede 1p/19q-codeletions [11, 23–25], the divergent IDH1 mutations may suggest the synchronous development of two independent low grade gliomas whose distribution is consistent with the reported anatomic distribution and prevalence of mutant IDH1 isoforms thus far.