The ultrastructural study of primary intracranial germ tumors

We describe here ultrastructural and clinicopathological features of five primary intracranial germinomas. By electron microscopy, two major tumor components were defined as large, well differentiated tumor cells and non-neoplastic cells such as macrophages, astrocytes and lymphocytes. Nuclei of tumor cells were round to oval, often presented irregularly contoured nuclear membranes with oval indentations and, occasionally, cytoplasmic invagination. Some of them constituted unusual conformational changes of nuclear membranes rarely described as intranuclear pockets. Desmosome-like intercellular junctions were observed in several neoplastic cells. The nucleoli were composed of a loose, fragmented nucleolonema, whereas elongated, anastomosing and rope-like nucleolonemas, described previously as characteristic for germinomas were not seen. Most tumor cells had villous cytoplasmic projections sometimes intermingled with similar projections of macrophages. Cytoplasm contained a moderate number of mitochondria, a few lysosomes, annulate lamellae, centrioles and glycogen particles. The other distinct components of tumor were lymphocytes, macrophages and astrocytes. Scattered astrocytes typically contained abundant glial filaments adjacent to primary tumor cell. A filopodia-like processes of macrophages often interspersed between other cells, were very prominent features of germinomas. Small lymphocytes were found scattered between the tumor cells, single or in clusters.