IDH1 and oligodendroglioma: In accordance with previous findings for histologically classified oligodendrogliomas [10, 71] and gliomas in general [19], we observed a large 1p/19q subgroup characterized by concurrent 1p/19q co-deletion and IDH mutation, an intermediate IDHme subgroup of tumors that mainly show an IDH mutation but no commonly overrepresented gene copy number alterations, and a small 7a10d subgroup showing a concurrent duplication of chromosome 7 and a deletion of chromosome 10 where most tumors lacked IDH mutations.