BSG and glioblastoma: Comparing the presence of proteins in glioblastoma cyst fluid with control CSF, a significant difference was found for 51 peaks. Twenty-eight proteins were present in glioblastoma but absent in CSF. Glial fibre acid protein (GFAP) (49 880 Da) lies in the 0·3% range of the 49 916 peak and VEGF121 (17 219 Da) in the range of the 17 224 peak. The molecular mass of 19 899 Da corresponds to the ferritin light chain. The protein basigin was detected at 40 211 Da in recurrent glioblastoma when compared to glioblastoma cyst fluid (data not shown)