Symptomatic hypophyseal granular cell tumour: endocrinological and clinicopathological analysis.

We report a case of a hypophyseal granular cell tumour (GCT) presenting with visual failure and hyperprolactinaemia (serum prolactin level, 274 ng/ml; normal, < 10). Magnetic resonance images demonstrated an intrasellar mass with anterosuperior extension. As the patient had chronic renal failure (CRF) and hyperprolactinaemia is frequent in CRF patients, a firm preoperative diagnosis of prolactinoma could not be made. Transsphenoidal removal of the tumour resulted in improvement of both vision and serum prolactin. Histopathological analysis of the surgical specimen revealed GCT. A cell kinetic study, the first such report for this type of tumour, revealed a relatively high Ki-67 staining index of 3.2%. On electron microscopy, numerous intracytoplasmic granules with various electron densities were demonstrated. Moreover, cell-processes extending from the granule-rich cytoplasm contained intracytoplasmic filaments but few granules, suggesting that the filament-rich cells, which are occasionally seen in GCT tissues, are essentially identical to the granule-rich cells in origin.