Infiltrating astrocytomas account for almost 80% of adult primary brain tumors. The usual location is cerebral hemispheres and the most commonly affected age group is 4th to 6th decades. The histologic spectrum ranges from diffuse fibrillary astrocytomas (WHO Grade II; shown in this image), through anaplastic astrocytomas (WHO Grade III) to Glioblastoma (WHO Grade IV). WHO Grade I is reserved for Pilocytic astrocytomas. The tumor shown here is WHO Grade II astrocytoma and it shows slight increase in the number of glial cells, mild nuclear pleomorphism, and a network of delicate astrocytic processes giving a fibrillary appearance to the background.