Tihan et al. found GFAP is consistently immunopositive in 94/94 pilocytic astrocytoma in which 90/94 showed more than 50% staining in the neoplastic cells (category 3 and 4), 2/94 showed immunostaining in 25–50% of the neoplastic cells (category 2), and the remaining 2 cases showed immunostaining in less than 25% of the neoplastic cells (category 1) [5]. This evidence concerns the gene GFAP and pilocytic astrocytoma.