Cytokeratin immunohistochemical study of epithelial cysts in the central nervous system: with special reference to origins of colloid cyst of the third ventricle and Rathke's cleft cyst in the sella.

A variety of epithelial cysts in the central nervous system were examined immunohistochemically for expression of cytokeratins. Colloid cysts, Rathke's cleft cysts and epithelial cysts in the spinal canal expressed complex type cytokeratins, while enterogenous cysts and neuroectodermal cysts showed only simple type cytokeratins. Colloid cysts showed a pattern of cytokeratins similar to that of upper respiratory tract which is endodermal in origin. In contrast, Rathke's cleft cysts showed a pattern of cytokeratins similar to that of the adenohypophysis and salivary gland which are ectodermal in origin. The CK immunohistochemical studies are discussed with regards to diagnostic significance and origins of their cysts.