A Case of a Neurohypophyseal Germinoma Misdiagnosed as a Pituitary Adenoma : Usefulness of a Gallium-67 Citrate Scintigram for Diagnosis

The author reports a rare case of a germinoma in a hypothalamoneurohypophyseal axis which was misdiagnosed as nonfunctioning pituitary adenoma. The patient, a 32-year-old male, was admitted to hospital because of diplopia and bi-temporal hemianopsia but without diabetes insipidus. A subsequent endocrinological exam uncovered panhypopituitarism, although the AFP and HCG were within normal range. A skull X-ray showed destruction of sella turcica and dorsum sellae, and CT scans revealed a homogeneously enhanced intrasellar tumor with a suprasellar and bi-lateral intracavernous extension. MRI showed an enhanced dumbbelled-shaped mass that had grown suprasellarly along the pituitary stalk through the diaphragmatic foramen but no normal pituitary gland, and a whole-body ^ Ga citrate study showed an abnormal accumulation in only the intracranial tumor region. A histopathological investigation by transsphenoidal exploration revealed a pure germinoma. After radiotherapy of 3.6 Gy, MRI revealed a transient enlargement of the tumor in the cavernous sinus. Radiotherapy was continued and the patient received a course of 50 Gy over 5 weeks and then was discharged. MRI and a ^ Ga citrate study revealed the complete remission of this tumor. Up to now, a positive ^ Ga accumulation has not been reported in a primary intracranial germinoma. Thus, a ^ Ga citrate study of such tumors is recommended, since it may provide a preoperative clue to differentiate between a sellar germinoma and pituitary adenoma.