IDH1 and gliosarcoma: Regarding the variants of glioblastoma, 4 were giant cell type, 1 of which was IDH1 positive positivity for IDH1. Two were gliosarcomas, both were positive; also the 2 glioblastomas with primitive neuroectodermal tumor (PNET) components were positive for IDH1 with granular rather than diffuse cytoplasmic staining.