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Cellular localization of cytokeratin and glial fibrillary acidic protein (GFAP) was examined in two normal choroid plexuses and five choroid plexus papillomas by the peroxidase-antiperoxidase (PAP) method and double immunofluorescence (IFL) microscopy. Cytokeratin was observed in the majority of epithelial cells in all samples of normal and neoplastic choroid plexuses. On the other hand, GFAP was observed in some of the constituent epithelial cells in two cases of papilloma. Most of these GFAP-positive papilloma cells were simultaneously positive for cytokeratin, as could be seen by the PAP stainings of serial sections and by the double IFL stainings of the same sections. From these findings, it was suggested that normal and neoplastic choroid plexus epithelial cells usually express cytokeratin and that some of the neoplastic cells can simultaneously express both cytokeratin and GFAP.

Two cases of medulloblastoma are described which show positive immunostaining for glial fibrillary acidic protein (GFAP) in many cells. The surgical and autopsy specimens were examined by the indirect immunoperoxidase method. Positive staining for GFAP was demonstrated in the small, round to polygonal cells in both surgical specimens and in the small spindle cells in the autopsy specimen of one case. In the small, round to polygonal cells positive GFAP was shown as a perinuclear brown rim or intracytoplasmic brown droplet. In the small spindle cells, the cytoplasm and the polar processes were stained. Except for GFAP staining, these positive cells were morphologically indistinguishable from the accompanying unstained cells, indicating that GFAP was expressed in the medulloblastoma cells. Considering that GFAP is specific for astrocytes, these findings suggest the potential of astrocytic differentiation in the neoplastic cells of these medulloblastomas. The findings obtained in other 28 medulloblastomas examined in parallel are also discussed briefly.

Thirteen patients with malignant brain tumors, 12 anaplastic gliomas and one metastatic tumor, received repeated intratumoral injections of an immunopotentiator, Picibanil, prepared from streptococcus pyogenes. All patients tolerated this therapy; morbidity rates were acceptable. Significant tumor regression was noted on computerized tomography scanning for 6 of 12 patients for whom scanning was performed. Histologic examination of the post-therapy specimens obtained from 8 patients revealed that inflammatory reactions were evoked in all of the tumors, although the extent of inflammatory changes varied from patient to patient and mostly was localized to an area surrounding the intratumoral tubes.

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