The ultrastructural study of primary intracranial germ cell tumours

We describe here ultrastructural and clinicopathological features of five primary intracranial germinomas. By electron microscopy, two major tumour components were defined as large, well differentiated tumour cells and non-neoplastic cells such as macrophages, astrocytes and lymphocytes. Nuclei of the tumour cells 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. Nucleoli were composed of a loose, fragmented nucleolonema whereas elongated, anastomosing and rope-like nucleolonemas, described previously as characteristic for germinomas were not seen. Typically, the cytoplasm contained glycogen particles. Most tumour cells had villous cytoplasmic projections sometimes intermingled with similar projections of macrophages. Scattered astrocytes typically containing abundant glial filaments were adjacent to primary tumour cells.