GFAP and astrocytoma (excluding glioblastoma): Interestingly, studies that find differences in GFAP expression between astrocytoma grades report on a decrease of general GFAP levels with increasing astrocytoma grade, but higher levels of GFAPδ are found in grade IV astrocytoma compared to grade I (Andreiuolo et al., 2009), grade II (Brehar et al., 2014), and grade I, II, and III (Choi et al., 2009).