Findings at time of initial resection. A) Pre-resectionT1-postgadolinium magnetic
resonance imaging, B) H&E-stained section, interface of
classic-appearing and anaplastic-appearing regions. C) Higher resolution
H&E-stained section, region with classic features of pilocytic
astrocytoma. D) Higher resolution H&E-stained section, anaplastic
region. E) GFAP immunohistochemical staining shows strong diffuse positivity in
classic pilocytic regions (E), but only scattered positive cells in anaplastic
regions (F). On p16 immunohistochemical stains, the regions with classic
features of pilocytic astrocytoma demonstrate diffuse positivity (G), while
anaplastic regions demonstrate loss of p16 expression (H).