Suprasellar germinoma masquerading as lymphocytic hypophysitis associated with central diabetes insipidus, delayed sexual development, and subsequent hypopituitarism.

We report the case of an 18-year-old woman with suprasellar germinoma masquerading as lymphocytic hypophysitis, which was associated with central diabetes insipidus, delayed sexual development, and hypopituitarism. Magnetic resonance imaging revealed an enlarged pituitary gland, thickened pituitary stalk, and a mass lesion in the inferior hypothalamus; these findings are typical of lymphocytic hypophysitis. Despite the administration of prednisolone therapy for 3 months, an enlarged irregular cystic mass lesion developed in the pituitary stalk and inferior hypothalamus. Open cranial surgery of the posterior pituitary revealed the presence of a germinoma. Therefore, chemotherapy and stereotactic radiation therapy were administered, resulting in complete remission of the germinoma. This case illustrates that the presence of an intrasellar mass lesion in association with pituitary stalk thickening can often cause difficulties in differential diagnosis. We believe that lymphocytic hypophysitis in pubertal children may be the first sign of a host reaction to an occult germinoma.