This is a pilocytic astrocytoma with anaplasia.

The patient underwent resection and fenestration of the left frontoparietal tumor via a left parietal craniotomy. The gross pathologic specimen revealed tan-pink soft tissue fragments. Histopathologically, the tumor was noted to be a glial neoplasm with moderately to markedly increased cellularity and multifocal microscopic infiltrative growth into adjacent cortex. The lesional cells were ovoid or round, displaying nuclear hyperchromasia, increased nuclear to cytoplasmic ratio, occasional multinucleation and identifiable mitoses, with up to 6 mitoses in 10 high power fields. Rare apoptotic bodies and microcalcifications were present. Rosenthal fibers and eosinophilic granular bodies were not seen. On immunohistochemistry, the lesional cells were positive for GFAP, Olig2 (strong diffuse), vimentin, SOX10, synaptophysin and CD34 (weak and multifocal). ATRX was positive/retained and a subset of tumor cells were positive for p53 with moderate to strong staining intensity. Ki-67 proliferation index was 7.3% (51/699). The neurofilament-positive neurites were multifocally seen in the tumor, indicating microscopic infiltration.