Granular cell tumors. Rare tumors of the neurohypophysis

Abstract Granular cell tumours of neurohypophysis are rare. These tumours are more often encountered as incidental autopsy findings seen in up to 17% of unselected adult autopsy cases. There are few reports of parasellar granular cell tumours large enough to cause symptoms. We present three cases of neurohypophysis granular cell tumour and a review of the literature. In one patient, the asymptomatic granular cell tumour was incidentally discovered at surgical removal of a corticotroph microadenoma. The remaining 2 patients had a symptomatic tumour which caused neurological symptoms such as visual disturbance and headaches and endocrine disorders such as hypopituitarism or hyperprolactinaemia. In these 2 cases, computerized tomography showed a well-circumscribed, contrast-enhanced, intrasellar and suprasellar mass. Magnetic resonance imaging demonstrated an isointense gadolinium-enhanced mass in T1-weighted images. Transsphenoidal partial resection was performed and histology was interpreted as a granular cell tumour. The immunohistochemical study was positive for glial fibrillary acidic protein (GFAP) and neuron specific enolase (NSE) in 1 of the 2 tumours and positive for S100 protein and vimentin in both tumours but negative for CD68. The histogenesis of neurohypophysis granular cell tumours is still controversial but ultrastructural and immunohistochemical studies support the theory that they may arise from pituicytes, the glial cells of neurohypophysis. Management of these benign, slow-growing, tumours is based mainly on neurosurgical resection. Data from the literature do not support a beneficial effect of postoperative radiation therapy on postoperative recurrences.