Non-adenomatous pituitary tumours mimicking functioning pituitary adenomas

Objective: Pituicytomas and granular cell tumours (GCTs) of the neurohypophysis are considered non-adenomatous neoplasms in the sellar region. The association between hormone hypersecretion and the tumours is seldom discussed and unclear. Therefore, we attempt to investigate this association based on our experience and a review of the literature.Methods: We report three patients who presented with Cushing's syndrome- or acromegaly-like symptoms at our institution. They underwent transsphenoidal surgery for suspected pituitary adenomas, which were subsequently diagnosed as pituicytomas or hypophyseal GCTs following histological and immunohistochemical analysis. We also review previously reported relevant cases of pituitary non-adenomatous tumours in the literature.Results: Four cases of Cushing's syndrome with pituicytoma and one case of acromegaly with a GCT have recently been reported. In the three cases presented here, one patient with Cushing's syndrome and one patient with acromegaly also had a pituicytoma, while the second patient with acromegaly had a GCT.Conclusions: Rather than mere coexistence of non-adenomatous pituitary tumours with hypersecretory adenomas or hyperplasia, alternative causes for the observed symptoms maybe the presence of some unidentified substances produced by the tumours that stimulate the adenohypophysis to secrete pituitary hormones. The glial cells of the pituitary gland may play an important role in oncogenic differentiation and regulation of the release of hormones. Therefore, attention should be focused on investigating the origin and functions of glial cells.