[Primary intracranial germ cell tumor with abnormal high value of alpha-fetoprotein after the radiation therapy].

A 7-year-old boy was admitted to Hokkaido University Hospital complaining of headache and vomiting. On admission he was slightly confused and presented Parinaud's sign. CT scan revealed abnormal high density mass with contrast enhancement effect at the pineal region and obstructive hydrocephalus. Laboratory studies showed the normal value of human chorionic gonadotropin and no trace of alpha-fetoprotein. Germinoma was most suspected based on the findings of CT scan and laboratory studies. The radiation therapy was carried out for a month and CT scan taken after the radiation therapy revealed marked reduction of the size of the tumor at the pineal region, and he was discharged. But he was re-admitted 3 months after the discharge complaining of headache and vomitting again. CT scan showed the recurrence of the tumor and laboratory studies showed abnormal high value of A.F.P. After the ventriculo-peritoneal shunt, the sub-occipital craniectomy was performed by the Stein's approach, and the tumor was removed. Pathologically the tumor was a typical yolk sac tumor. This case is a very interesting case because it suggests an alternation of the element of the germ cell tumor by the radiation therapy. At first admission, germinoma was the main element of the tumor judging from the effectiveness of the radiation therapy and laboratory studies. But the main element of the tumor seemed to have changed to yolk sac tumor after the radiation therapy. The relation between the tumor markers and the types of the germ cell tumor and histopathological characters of the intracranial germ cell tumor were discussed.