EXPERIMENTAL STUDIES ON BRAIN TUMORS

Summary 1. Experimental induction of gliogenous tumors was made by implanting methylcholanthrene pellets into the brain of laboratory animals. Two hundred and forty‐two mice of C3H, ddN, CF1, CFW, C57BL strain and 212 rats of Wistar and Donryu strain were employed in this experiment. A total of 112 mice and 21 rats were found to have tumor. By histological examinations, 39 tumors in mice and 13 in rats were classified as gliomas, 8 tumors in mice and 1 in rat as mixed glioma and sarcomas, and the others as mesenchymal tissue tumors. 2. Experimantally produced tumors were successfully transplanted into the brain and the subcutis of animals of the same strain. They were capable of subsequent transfer through a number of generations. The transplants recapitulated the histological features of the parent tissue, but they became less pleomorphic and more undifferentiated in appearance. Experimental gliomas were also successfully transplanted into the heterogeneous strains. 3. By applying the criteria employed in the classification of human glioma, the experimentally produced gliomas were subclassified into glioblastoma, oligodendroglioma‐, astrocytoma‐, and ependymoma‐like tumors. Glioblastomas comprised the majority of total gliomas. This type of glioma was closely mimiced the corresponding histological type of gliomas in man. Gliomas of adult tissue were classified according to the histology in routine sections. By special impregnation techniques and by electron microscopy it became evident that the constituent cells of this type of tumor appeared more or less anaplastic. It is, therefore, not easy to subclassify the experimental gliomas into various distinct histological types as those in man. 4. The frequent production of mixed gliomas, and gliom as mixed with sarcoma was 5. Tumors of mesodermal origin were also produced in die experiments. The frequency of their production constitutes one of the characteristic features of experimental tumors in mice. It is argued mat intracerebral vessels and meninges are possible sources of die experimental tumors of mesodermal origin. 6. Decisive evidences about the problem of topographical peculiarities in different histological types of experimental gliomas were not obtained in this experiment. There was no tumor incidence with the histology of medulloblastoma in man. Therefore, this study failed to afford any evidence that medulloblastoma is a neuroblastoma derived from the adult neurons in the granular layers of the cerebellar cortex.