[Pituitary germinoma and lymphocytic hypophysitis: a pitfall. Report of two cases].

We report two cases of pituitary germinomas in two young men aged 13 and 21, revealed by insipidus diabetes associated with visual field defects or hypopituitarism. Neuroimaging of the first case was initially normal, then showed an infiltration of the stalk; the lesion of the second case appeared as a nodular thickening of the stalk and subsequently a pituitary infiltration. Histologically they mimicked lymphocytic infundibulo-neuro-hypophysitis (LINH) or lymphocytic hypophysitis (LH), the large tumoral clear cells being out-numbered by the heavy inflammatory stroma or mistaken for macrophages. Only the immuno-staining by placental alkaline phosphatase led to the diagnosis. In these tumours, immunostaining positive for CD-117 and negative for CD30, confirmed the diagnosis and should allow the distinction of pituitary germinoma from other germ cell tumours as recently described in the testis, and may have a therapeutic interest.