Immunohistochemical study of Rathke's cleft cyst.

An immunohistochemical study was made of ten cases of asymptomatic and three cases of symptomatic Rathke's cleft cyst. The cysts in the asymptomatic cases had monolayer columnar or cuboidal epithelium. Within the epithelium, cells which were positive for at least one of the pituitary hormones were found. The rate of positive reactions for these six pituitary hormones was between 70% and 100%. In contrast, the cysts in the symptomatic cases had an epithelium which was partly stratified squamous and partly squamous epithelium, and none of the pituitary hormones were found in them. Therefore, when a Rathke's cleft cyst enlarges to the extent that clinical symptoms are produced, we consider that changes have already occurred in structure and function of the cyst epithelium. In addition, we believe there is a tendency for monolayer epithelia to undergo squamous metaplasia and for cells which are positive for pituitary hormones to change into non-granulated cells.