Folliculo-stellate cells in pituitary adenomas of patients with acromegaly

Pituitary adenoma tissue from patients with acromegaly (n = 286) was obtained by surgery and examined for folliculo-stellate cells by immunostaining for S100 protein. The number of immunostained cells varied from one adenoma to another. A hundred and ninety-eight pituitary adenomas (69%) contained S100 protein positive cells corresponding to folliculo-stellate cells (FSC): in 100 cases (35%), only few sparse FSC were found, in 43 cases (15%) FSC were scattered throughout the adenoma, and in 55 cases (19%) there was an abundance of FSC. There were no significant differences regarding sex or age of the patients. The relative amount of FSC varied among different adenoma types. Plurihormonal adenomas showed the highest FSC density, whereas the majority of monohormonal adenomas contained only few or no FSC. Patients with pituitary adenomas containing scattered FSC had a significantly higher preoperative mean GH level than patients with pituitary adenomas not having FSC. There was a negative correlation between the FSC density in adenoma tissue and the preoperative mean PRL level. There was no correlation between the tumour size and the amount of FSC. Our data indicate no effect of the duration of symptoms on the FSC density and do not suggest a correlation between FSC density and the percentage of a certain hormone-secreting cell type.