A Case of Pituitary Germinoma Misdiagnosed as Lymphocytic Hypophysitis

Abstract

Abstract Pituitary germinomas are difficult to be differentiated from lymphocytic hypophysitis due to similar clinical, radiological and even histological findings. However, it is of great importance to make the distinction between them because of different therapeutic approaches 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 pan-hypopituitarism. Magnetic resonance imaging (MRI) of the pituitary which first had shown mild pituitary enlargement, revealed a pituitary mass of unusual feature after 1 year. Pathological 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 histological examination confirmed the diagnosis of germinoma. Subsequently, the patient underwent radiotherapy, and complete remission was achieved; however, pan-hypopituitarism 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.