IDH1 and glioblastoma: The latest fifth edition recently refined the diagnosis of glioblastoma by adopting a multilayered integrated approach incorporating new molecular criteria such as TERT promoter mutation, EGFR amplification, or chromosomal 7 gain/chromosomal 10 loss for IDH-1 wildtype astrocytomas.51 Since the majority of lower grade astrocytomas in Hong Kong were not subject to such testing during the review period, a proportion of tumors would have been inadvertently excluded from the Hong Kong GBM Registry.