Fig. 2

a H&E section showing some peripheral infiltration in this astrocytoma with mild nuclear atypia. b Smear preparation during the intraoperative microscopic examination, showing mildly atypical astrocytes with prominent bipolar piloid processes. c Dense, relatively hypercellular area with mild nuclear atypia and occasional multinucleated cells with peripheral nuclei (“penny on a plate”). d Focal oligodendroglioma-like morphology, with perinuclear clearing and round nuclei with speckled chromatin. e Extensive cytoplasmic GFAP immunostaining. f Low MIB (KI67) proliferation labeling index of 1–2%