第3脳室巨大悪性脈絡叢乳頭腫の1例—免疫組織化学的，電顕的検討

A CASE OF LARGE MALIGNANT CHOROID PLEXUS PAPILLOMA IN THE THIRD VENTRICLE: IMMUNOHISTOCHEMICAL AND ULTRA-STRUCTURAL STUDIES

　抄録　乳幼児に発生したきわめてまれな第3脳室内の巨大悪性脈絡叢乳頭腫（脈絡叢癌）の1例を報告した。症例は1歳2か月の女児．視力障害，歩行障害にて発症。頭部CT, MRIで第3脳室内に径約5cmの腫瘤を認めた。側脳室経由で亜全摘出後放射線照射を施行した。組織は光顕的に，乳頭状配列を示す部分と乳頭状構造を失って退形成を示す部分がみられた。腫瘍細胞は異型性が強く，多数の核分裂像，小さな壊死巣を散在性に認めた。免疫染色では多くの腫瘍細胞はケラチン陽性であった。GFAPは腫瘍細胞，間質ともに陰性であった。電顕的には腫瘍細胞の胞体内には遊離リボゾーム，グリコーゲン顆粒，粗面小胞体が多くみられた。管腔側の細胞には太い棍棒状あるいは球形の異常なmicrovilliを多数認め，その内部にはグリコーゲン顆粒が豊富にみられた。また腫瘍細胞間には細胞間接着装置がしばしば認められた。腫瘍の基底部においては，腫瘍細胞と間質の境界部に基底膜が恒常的に存在していた。以上より悪性脈絡叢乳頭腫と診断されたが，特に本腫瘍と上衣腫との鑑別診断には免疫組織化学的，電顕的検索がきわめて有用であった。

A case of malignant choroid plexus papilloma (choroid plexus carcinoma) originated in the third ventricle is reported.

A 14-month old girl was admitted to our depart-ment with two-month history of impaired vision and gait disturbance. Neurological examination on admission disclosed a lethergy, blindness, and left hemiparesis. Computed tomographic (CT) scan and magnetic resonance imaging (MRI) demon-strated a large contrast-enhancing mass, approxi-mately 5 cm in diameter, in the region of third ventricle, extending to the bilateral lateral ventri-cles. The patient had gross total removal of the tumor via lateral ventricle route, and received 40 Gy of postoperative radiation therapy. Light mi-croscopically, the tumor was composed of epithelial cells showing both papillary and poorly differen-tiated pattern. There were considerable cellular pleomorphism, frequent mitoses, and occasional ne-croses. Immunohistochemically, anti-keratin anti-body was detected within majority of neoplastic cells. Both neoplastic epithelial cells and stroma showed negative reaction to anti-GFAP antibody. Ultrastructurally, the shape of the nuclei varied from ovale to irregular with many indentations. The chromatin was clumped around the periphery of the nuclei. The neoplastic cells contained nu-merous free ribosomes, glycogen granules, and rough endoplasmic reticulum. The apical cell sur-faces showed various size of club-like or roundish microvilli filled with glycogen granules, and rarely 9+2 cilia. Elongated junctional complexes were occasionally seen near the apical ends. The basal portions of the cells had a continuous basement me-mbrane. These immunohistochemical and ultrast-ructural findings were comparable to the choroid plexus papilloma with malignant features. The present study suggests that the immunohistochemi-cal and ultrastructural observations are of great significance in the strict diagnosis of malignant choroid plexus papilloma.