Immunohistochemical differential diagnosis of benign cysts in the central nervous system.

This report concerns the immunohistochemical characterization of 6 cases of thin-walled cysts in the central nervous system (enterogenous cyst, paraphyseal neuroepithelial cyst, Rathke's cleft cyst and arachnoid cyst). Antibodies to glial fibrillary acidic protein (GFAP), S-100 protein, epithelial membrane antigen (EMA), carcinoembryonic antigen (CEA), keratin (KER) and vimentin (VIM) were used. The enterogenous cyst was positive for KER, EMA and CEA. The neuroepithelial cyst of paraphyseal origin was positive for KER and S-100. The three Rathke's cleft cysts were positive for KER and EMA, but negative for S-100 and CEA, and the arachnoid cyst was positive for EMA and VIM. A unified concept and classification of the types of cysts studied based on immunohistochemical assays are proposed.