Ganglioglioma of the neurohypophysis with secretion of vasopressin.

A patient with a ganglioglioma of the neurohypophysis developed the syndrome of inappropriate antidiuretic hormone secretion (SIADH). We present the case and describe its microscopic and ultrastructural features. Malignant neoplasms were thought to be the main cause of ectopic production of vasopressin. Head trauma, infection, or drugs, however, can also induce hypersecretion of vasopressin. Mechanical compression of the pituitary stalk can lead to an excessive antidiuretic hormone (ADH) release by affecting the inhibitory system. Primary neuroendocrine tumors of the hypothalamic-neurohypophyseal system are extremely rare. We demonstrate the presence of vasopressin in the tumor cells by immunocytochemistry. This represents the first case of SIADH caused by a tumor of the neurohypophysis.