In GBM, however, AQP4 becomes disorganized—often redistributed throughout the astrocytic membrane or even overexpressed in tumor cells—thereby compromising tumor-associated perivascular fluid transport (Noell et al., 2012; Mou et al., 2010) as illustrated schematically in Figure 3 and histologically in Figure 4. The gene discussed is AQP4; the disease is neoplasm.