Primary intrasellar germinoma

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Abstract
The case presented is the 1st of its type in which a germinoma was shown to arise primarily within the pituitary fossa, causing uniform expansion and erosion of the sella turcica. At pneumoencephalography, the tumor circumference was outlined by air in the suprasellar cistern. This is unlike most of the cases in the literature where a filling defect in the 3rd ventricle, with obliteration of the cistern, was described. Initially, this case was thought to be a chromophobe adenoma, but attention was drawn to the possibility of germinoma following profuse diuresis in response to preoperative administration of corticosteroids. Diabetes insipidus is induced when the neurohypophysis and hypothalamus are affected without interruption of function of the adenohypophysis. Symptoms of diabetes insipidus may begin to disappear if the function of the adenohypophysis is involved. If the function of the adenohypophysis and neurohypophysis are affected from the beginning, diabetes insipidus may not be apparent clinically, but even in such a case, it is unveiled upon administration of steroids. The tumor invaded the anterior pituitary and then spread upward to the hypothalamus. This would explain the absence of diabetes insipidus until steroids were given. That the suprasellar cistern was outlined by air at pneumoencephalography would not rule out microscopic invasion of the hypothalamus. Retrospectively, one can detect a few thick bands of tumor tissue extending across the cistern into the hypothalamus.