Adult cerebellar glioblastomas (cGBM) are rare and their characteristics remain to be fully described. We analyzed the characteristics of 17 adult patients with cGBM and compared them to a series of 103 patients presenting a supra-tentorial glioblastoma (stGBM). The mean age at GBMc diagnosis was 53.4 years (range 28-77). A history of neurofibromatosis type I was noted in 3 patients. cGBM were hemispheric in 10 patients (58.8%), only vermian in 4 patients (23.5%), and both vermian and hemispheric in 3 patients (17.7%). A H3 K27M mutation was identified in 3/14 patients, a TERT promoter mutation in 3/14 patients and a methylated MGMT promoter in 3/14 patients. None of the patients (0/14) harbored an EGFR amplification, an IDH or a BRAF mutation. Association with neurofibromatosis type I and H3K27M mutations were mutually exclusive. Compared with stGBM, cGBM occurred in younger patients (53.4 vs. 63.2, p = 0.02), were more frequently associated with neurofibromatosis type I (18 vs. 1%, p = 0.009) and with a H3 K27M mutation (21 vs. 3%, p = 0.02). They also tended to have a more frequent multifocal presentation at diagnosis (21 vs. 4.3%, p = 0.06), more frequently resulted in leptomeningeal or intra-axial metastasis (44.5 vs. 5%, p = 0.002) and were associated with a shorter median overall survival (5.9 vs. 14.2 months, p = 0.004). The present study suggests that adult cGBM differ from their supra-tentorial counterpart and constitute a heterogeneous group of IDH wild-type gliomas with at least two subgroups, one associated with H3K27M mutations and the other with neurofibromatosis type I.
Keywords: Cerebellar glioblastoma; Histone H3.3 K27M; Leptomeningeal dissemination; Multifocal glioblastoma; Neurofibromatosis type I.