IL13RA2 and astrocytoma (excluding glioblastoma): Since GBM (defined as astrocytomas WHO grade IV) displayed the highest levels of IL13Rα2 expression, we tested whether astrocytomas (WHO II and III) over-expressed IL13Rα2 more frequently than histologically distinct oligoastrocytomas or oligodendrogliomas of the same grade (WHO II and III).