Ultrastructural study of the medulloblastoma in tissue culture.

The electron microscopic features of the early phases of growth of the medulloblastoma maintained in vitro are described. The predominant early growth is comprised of small migrating cells with large nucleocytoplasmic ratio, few organelles and prominent neuritic processes containing abundant microtubules. These cells compare favorably with the cells of the primitive external granular layer of the cerebellum and cells cultivated in vitro from the fetal cerebellar cortex previously described. In addition astrocytes containing 70 to 90 A cytoplasmic filaments were commonly found in these cultures. Undifferentiated cells and cells with cilia were present in the explant proper. Cells with processes containing large dense core vesicles were also present in the explant proper suggesting the presence of neuronal differentiation. Our studies support the concept that the medulloblastoma is derived from primitive neuroectodermal cells. In addition it also suggests that astrocytic and neuronal differentiation may occur in this neoplasm in vitro.