TP53 and astrocytoma (excluding glioblastoma): Recently, the identification of a number of immunohistochemical markers, including not only p53 but also mutated isocitrate dehydrogenase 1 (IDH1R132H) and alpha‐thalassemia X‐linked intellectual disability (ATRX), and molecular markers including epidermal growth factor receptor (EGFR) using, for example, fluorescence in situ hybridisation, has been shown to be an indispensable tool for the diagnosis of infiltrating astrocytomas13; this immunohistochemical and molecular testing will be of great help in the differential diagnosis of PML vs infiltrating astrocytomas.