The pathogenesis of cysts accompanying intra-axial primary and metastatic tumors of the central nervous system.

Recent reports have suggested that cyst formation accompanying astrocytomas in the central nervous system (CNS) is due to an edematous process caused by blood-brain barrier (BBB) disruption and not a result of necrosis. This study is performed to investigate whether the hypothesis of cyst formation based on BBB disruption also applies to various pathologically different intra-axial gliomatous tumors and metastases. By chemical analysis, using immunokinetic nephelometry, isoelectric focussing, cellulose acetate electrophoresis and a biuretic method, the concentrations of albumin, immunoglobulin G (IgG), IgA, alpha2-macroglobulin, IgM and total protein were measured and proportions of concentrations of these proteins were compared in cyst fluid, blood plasma and cerebrospinal fluid (CSF). Our data, based on the chemical analysis of cyst fluid and blood plasma of 37 patients, including 2 ependymomas (one cerebral; one thoracic), 3 oligodendrogliomas, 4 hemangioblastomas, 5 cerebellar astrocytomas and 1 cervical, 1 giant astrocytoma grade one, 1 gangliocytoma, 1 neuroblastoma and 19 metastases (five lung-; two renal-; three breast-; one melanoma-; one thyroid metastasis and seven metastases of unknown origin) present high protein concentrations in the cysts with a highly similar spectrum of proteins in the tumor cyst fluid and blood plasma, suggesting a BBB disruption followed by exudation of plasma proteins into the brain parenchyma with formation of edema and transition of edematous tissue into a cyst accompanying the tumor. Although histopathologically different types of tumor tissue are involved, data suggests that the pathogenesis of cysts accompanying gliomatous tumors and metastases in the CNS is based on BBB disruption and consequent edema, as is the case in the formation of cysts in anaplastic astrocytomas.