[A case of large malignant choroid plexus papilloma in the third ventricle--immunohistochemical and ultrastructural studies].

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 department with two-month history of impaired vision and gait disturbance. Neurological examination on admission disclosed a lethargy, blindness, and left hemiparesis. Computed tomographic (CT) scan and magnetic resonance imaging (MRI) demonstrated a large contrast-enhancing mass, approximately 5 cm in diameter, in the region of third ventricle, extending to the bilateral lateral ventricles. The patient had gross total removal of the tumor via lateral ventricle route, and received 40 Gy of postoperative radiation therapy. Light microscopically, the tumor was composed of epithelial cells showing both papillary and poorly differentiated pattern. There were considerable cellular pleomorphism, frequent mitoses, and occasional necroses. Immunohistochemically, anti-keratin antibody 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 numerous free ribosomes, glycogen granules, and rough endoplasmic reticulum. The apical cell surfaces 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 membrane. These immunohistochemical and ultrastructural findings were comparable to the choroid plexus papilloma with malignant features.(ABSTRACT TRUNCATED AT 250 WORDS)