GFAP and astrocytoma (excluding glioblastoma): GFAP negative microcystic (Gullotta et al., 1985; Velasco et al., 1980) and necrotic areas (Tascos et al., 1982), and focal GFAP staining are more often seen in higher grade astrocytoma (Cras et al., 1988; Cruz‐Sanchez et al., 1992), whereas diffuse GFAP staining (Cruz‐Sanchez et al., 1992; Royds et al., 1986) and a dense fibrillary network with clear staining of processes (Peraud et al., 2003; Zamecnik et al., 2004) are more often seen in lower grade astrocytoma with one study specifically reporting on shorter processes in grade III and grade IV astrocytoma (Zamecnik et al., 2004).