Oligodendroglioma (ODG) are slower growing, lower grade gliomas associated with a distinct constellation of mutations, including gain-of-function mutations in IDH1/2, and chromosomal co-deletion of 1p/19q [124], with mutation of Capicua transcriptional repressor (CIC) in the retained chromosome also prevalent [171,172,173,174]. The gene discussed is IDH1; the disease is glioma.