Ultrastructural study of the pineal germinoma in vivo and in vitro.

The fine structure of a pineal germinoma was studied in tissue blocks and in tissue culture. The original tumor contained large primary tumor cells, lymphocytes, macrophages, plasma cells, and astrocytes. The large primary tumor cells were characterized by large nuclei, relatively scanty organelles, abundant glycogen, and junctional complexes. The neoplasm grew well in vitro and, with the exception of plasma cells, contained the same cell types found in vivo. The ultrastructural characteristics of the cells in vivo and in vitro were similar. In culture there were few large primary tumor cells. Macrophages, often involved in active phagocytosis, were prominent in the original tumor and were the most common cell type found in vitro. A tumor-associated immune response is postulated in this neoplasm.