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Figures 1~4 were taken from frozen sections, and were uploaded first. The remaining photos were taken from permanent sections, and were planned to be posted later. I uploaded and placed them in the same folder as the first 4 photos, and unknowingly posted all of them together. Now I know and will not make the same mistake again. Figures 1~12 show very classic features of a WHO grade I pilocytic astrocytoma. Figures 11~12 are taken from the cystic wall of the tumor. As you can see, neither eosinophilic granular bosies nor Rosenthal fibers are necessary for the diagnosis of pilocytic astrocytoma.

Figures 13~14 show Bergman gliosis of adjacent degenerated cerebellar cortex that may be confused with gliomatous involvement. This can be difficult to tell at intraoperative consultation. One helpful hint is its laminated appearance conforming to the pre-existing interface of molecular and Purkinje cell layers. If one or two residual Purkinje cells remain, the task will be a lot easier.