Pituitary germinomas are difficult to be differentiated from lymphocytic hypophysitis due to similar clinical, radiologic, and even histologic findings. However, it is of great importance to make the distinction between them because of different therapeutic approach of the two diseases. We report a case of neurohypophysial germinoma who initially was misdiagnosed as lymphocytic hypophysitis. The patient was a 26-year-old man who first presented with central diabetes insipidus and subsequent panhypopituitarism. Magnetic resonance imaging (MRI) of the pituitary which first had shown mild pituitary enlargement, revealed a pituitary mass of unusual feature after one year. Pathologic diagnosis of the lesion, biopsied through trans-sphenoidal route, was lymphocytic hypophysitis. Corticosteroid was initiated for him. Despite intensive treatment clinical symptoms worsened and the patient developed visual field defect. Follow-up MRI revealed enlargement of the pituitary mass with suprasellar extension and involvement of optic chiasm. Surgical resection of the mass was performed, and the second histologic examination confirmed the diagnosis of germinoma. Subsequently, the patient underwent radiotherapy, and complete remission was achieved; however, panhypopituitarism persisted. In conclusion, the possibility of neurohypophyseal germinoma should be considered in patients with the diagnosis of lymphocytic hypophysitis who do not respond to corticosteroid therapy.

Key words: Germ cell tumor, Pituitary germinoma, Lymphocytic Hypophysitis.