Further ultrastructural studies on reticulum cell sarcoma (microglioma) of the brain.

The ultrastructure of a primary reticulum-cell sarcoma (microglioma) of the brain was studied. The main or predominant tumor cells had a relatively abundant perikaryon with peripheral pseudopods and a moderate number of organelles. The nucleus was multilobulated and contained a prominent nucleolus. A second type, or phagocytic cell, had a similar structure but exhibited some distinctive features. The cytoplasm contained numerous lysosomes, phagolysosomes, occasional phagocytized whole cells and abundant organelles, especially Golgi complex. The nucleus was ovoid and nucleoli were smaller. This cell was considered to be a neoplastic element with a higher degree of differentiation. A third group of cells included lymphocytes with various degrees of maturation and/or differentiation as well as plasma cells exhibiting active protein synthesis. It is concluded that the ultrastructural features of the neoplasm are indicative of a reticulohistiocytic nature.