[Differential diagnosis and origin of epithelial cysts in the central nervous system--report of seven cases and review of literature].

Seven cases of epithelial cysts are presented with special reference to histological findings. Differential diagnosis and origin of the cysts are also discussed. Two are autopsy cases and 5 are surgical cases. Median age of the patients is 41 years. Three cysts are in the posterior fossa, 1 in the supratentorial region, 1 in both infra- and supratentorial regions and 2 in the spinal canal. On light microscopy, the type of cell lining the cyst wall and the presence of cilia and PAS-positive cells are studied. All cyst walls were lined by a single layer of cuboidal to columnar epithelium. Cilia was seen in 1 and PAS-positive cells were found in 5 out of 7 cases. On electron microscopy of the 4 cases available for study, continuous basement membrane and microvilli were observed in all cases. Coating material covering microvilli was noted in 2 cases. According to these histological findings, these cysts are classified as follows: 1 multiloculated cyst, 1 (respiratory) epithelial cyst, 3 (enterogenous) epithelial cysts, 1 ependymal lined cyst and 1 neuroectodermal cyst. Various non-neoplastic cystic lesions are found in the central nervous system, such as arachnoid cyst, ependymal cyst, colloid cyst, choroid epithelial cyst, neurenteric cyst, and Rathke's cleft cyst. Although histological difference between arachnoid cyst and other epithelium-lined cysts is relatively clear, the precise discrimination between other cystic lesions is difficult and controversial. Some authors have considered these cysts as a neuroectodermal origin because of their histological similarity with choroid plexus or ependyma.(ABSTRACT TRUNCATED AT 250 WORDS)