YKL-40 immunoreactivity is specifically detected at sites of brain barriers and entry points for microglia in the developing human brain and is known to be involved in angiogenesis, inflammation and is overexpressed in glioblastoma (brain cancer, GBM) (Lal et al., 1999; Nigro et al., 2005; Colin et al., 2006) and brain tissue and/or CSF in several neurological disorders that commence in the developing brain or/and involve dysfunction of brain barriers (Chung et al., 2003; Colton et al., 2006; Arion et al., 2007; Garbett et al., 2008; Bonneh-Barkay et al., 2010). The gene discussed is CHI3L1; the disease is glioblastoma.