FINE STRUCTURE OF MEDULLOBLASTOMA

Abstract

Thirteen cases of classical medulloblastoma and two cases of desmoplastic medulloblastoma were examined by electron microscopy. The classical medulloblastoma was composed of two types of tumor cells. The cells of the first type were characterized by the presence of a nucleus with a heavy chromatin net, as well as the presence of fine filaments (70-100Å across) and glycogen particles in their cytoplasmic processes. Cilia, microtubules, and intercellular attachment devices were occasionally observed in the cells of this type. The cells of the second type had a nucleus with an evenly distributed chromatin and one or two prominent nucleoli. Microtubules were seen in the cytoplasmic processes. The first-type cells appeared to retain the characteristics either of astrocyte or of ependymal cell, whereas the secondtype cells exhibited the characteristics of both oligodendroglia and neuron, the distinction between these two not being clear.
The cells of the desmoplastic medulloblastoma were similar in fine structural appearance to those of classical medulloblastoma but they showed a tendency to form clusters or rows which were separated from the connective tissue by a basement membrane, suggesting a neuro-ectodermal origin of this tumor. The term "circumscribed cerebellar sarcoma, " which has often been used for this tumor, should be dropped from the nomenclature.