血中および髄液中alpha-fetoprotein高値を示した大脳基底核germ cell tumorの1症例

GERM CELL TUMOR IN THE BASAL GANGLIA WITH ELEVATED SERUM AND CSF ALPHAFETOPROTEIN LEVELS

　抄録　頭蓋内原発germ cell tumorの好発部位は松果体部および鞍上部であり，大脳基底核に発生することは稀である。私達は12歳男子で右半身不全麻痺で発症し，血中および髄液中alpha-fetoprotein （AFP）高値を示した大脳基底核部原発germ cell tumorを経験した。開頭術によって得られた標本はtwo cellpatternのgerminomaを示し，抗AFP血清を用いた酵素抗体法により染色される細胞は認められなかったが，血中および髄液中AFPが高値を示したことから，残存している腫瘍内にendodermal sinus tumorが存在する可能性が考えられ，臨床的にはgerminomaとendodermal sinus tumorの混合腫瘍と診断した。放射線治療（lineac全脳照射5500 rads）により，血中AFPは27800ng／mlから607 ng／mlまで低下するとともに腫瘍の著明な縮小が認められた。治療後2ヵ月が経過した現在，腫瘍の再燃はなく，血中　AFP値も484ng／mlにとどまっている。この症例についての詳細，特に腫瘍の大きさ，およびAFP　値と治療の関連について報告し，文献的考察を加える。

Intracranial germ cell tumors usually locate either in the pineal region or in the suprasellar region or both. Primary occurrence of germ cell tumor in the basal ganglia is rare. To our know-ledge, only 17 cases have been reported in the literatures, and all the patients were Japanese. None of these patients presented elevated serum and CSF AFP levels in the literatures. We are reporting a patient with a germ cell tumor which developed in the left basal ganglia and showedhigh serum and CSF alpha-fetoprotein (AFP) levels.

The patient was a 12-year-old boy who had been completely well until five months prior to the first admission when he developed weakness of right extermities. On admission he showed a right hemiparesis of mild degree and right hype-sthesia. CT-scans demonstrated a homogenous high density area over the caudate head and the putamen on the left side. The anterior limb of the left internal capsule and a part of the posterior limb were also involved. The lesion was modera-tely enhanced by the contrast medium. Stereotaxic biopsy of the lesion was uncontributory and he was discharged for follow up. Five months later, CT-scans demonstrated the enlargement of the high density area with perifocal edema. Then we performed a craniotomy, and the tumor which was soft and dark red in colour was biopsied at the wall of the anterior horn of the left lateral ventricle. 1-Iistopathology of the specimen showed germinoma of two-cell pattern. Preoperative AFP levels in serum and CSF were 27800 ng/ml and 48000 ng/ml respectively. HCG and CEA were negligible. Although immunohistological study of the surgical specimen failed to demonstrate tumor cells which contained AFP, this germ cell tumor was clinically diagnosed as a mixed tumor con-sisted of germinoma and endodermal sinus tumor. Postoperatively he was treated with irradiation, 5500 rads to the whole brain and 2050 rads to the whole spine using 6 MeV lineac in conjunction with chemotherapy with bleomycin and vincristine. The level of serum AFP was decreased from 27800 ng/ml to 607 ng/ml by the treatment and the tumor was reduced in size remaining a ring-like enhancement in the left basal ganglia by the contrast medium. At present, two months after the therapy, the patient remains well with mode-rate hemiparesis and serum AFP level of 484 ng/ml.