Histopathologic features of the tumor. (a) Cellular and nuclear atypia, hyalinized vessels, a papillary pattern and a pseudorosette (top left corner) with the typical stout processes (× 200). Positive immunostaining against GFAP (b) and p53 (c) (× 400). Several tumor cells with positive immunoreactivity for the proliferative marker Ki-67/MIB-1 (d) with an index of 10% (× 400).Astroblastoma - a case report of a rare neuroepithelial tumor with complete remission after chemotherapy. Bergkåsa M, Sundstrøm S, Gulati S, Torp SH - Clinical neuropathology (2011 Nov-Dec). Not Altered. CC.