IDH1 and glioma: In grades 2 and 3 gliomas, IDH mutations seemed to be related to lower HMGB2 expression; however, in grade 4 astrocytomas, HMGB2 expression was significantly higher in A4IDHmut, which bear CDKN2A/B homozygous deletions [22,52], compared to GBMs at IHC.