Immunohistochemical study of folliculostellate cells in pituitary lesions.

This immunohistochemical study of the folliculostellate (FS) cells of the pituitary gland demonstrated that these cells have strong reactivity for S-100 protein, some reactivity for glial fibrillary acidic protein, keratin, and vimentin, and no reactivity for NSE and epithelial membrane antigen. An increased number of FS cells was seen at the margin of pituitary adenoma, abscess, and amyloid deposits, and in residual adenohypophysis after-hypophysectomy, whereas no FS cells were seen in the margin of metastatic tumor, Rathke's cyst, and both recent and old infarcts. Our findings affirm the supportive function of FS cells.