EXT1 and glioblastoma: On the other hand, Sethi et al. reported that 8 of 18 patients (44.4%) with pure class V LN exhibited bright granular GBM staining for EXT1/EXT2, while 2 of 14 patients (14.3%) with mixed class LN (class III/IV + V) also demonstrated GBM staining for EXT1/EXT2 [22].