Immunohistochemical study of folliculo-stellate cells in human pituitary adenomas

Folliculo-stellate (FS) cells were studied in 102 human pituitary adenomas by immunohistochemical techniques using antibodies to S-100 protein and intermediate filaments protein. In most pituitary adenomas there were few S-100-positive cells, in contrast, numerous FS cells were found in four of the 54 cases of non-functioning adenomas. Among glial fibrillary acidic protein (GFAP), keratin and vimentin, FS cells showed greatest affinity to vimentin. Stains for desmin or neurofilaments were always negative. Counterstains with GFAP and keratin could demonstrate a small number of double-labelled cells, but mainly disclosed two types of FS cells positive for either GFAP or keratin. Accordingly, FS cells were grossly subdivided into two types: GFAP-positive cells which might be neuroectodermal or glial in origin and keratin-positive cells which might be oral ectodermal or derive from the Rathke's pouch.