IDH1 and oligodendroglioma: Additionally, although this patient exhibited a heterozygous CDKN2A deletion, its clinical impact is expected to be limited, as hemizygous CDKN2A deletions have been reported not to significantly worsen overall survival or progression-free survival in IDH-mutant astrocytomas and oligodendrogliomas, CNS WHO grades 2 and 3 (31).