Primary cerebral reticulosis and plasma cell diffenentiation.

Cerebral proliferative and tumour forming reticulosis are primary pathologic processes of the brain originating in the perivascular adventitial cell. In these conditions this cell can transform into a histiocyte or microglial cell with characters of a macrophage. A reactive cell with endoplasmic reticulum, basement membrane and fibril forming properties, is also present (fibril forming reticular cell). The malignant tumours of the perivascular spaces (cerebral reticulosarcoma) are characterized by the presence of the dedifferentiated cells originating from the intraadventitial cell. Under both proliferative and tumour forming conditions this cell may transform into a cell rich in endoplasmic reticulum, sometimes charged with Russell bodies and corresponds morphologically to the protein-forming plasma cell. The properties of the intracerebral periadventitial cells are identical with those of the reticulo-histiocytic system described by ASCHOFF. As its structure and the elements into which it differentiats sharply differ from those of the cells belonging to the lymphocyte series the term malignant lymphoma of the brain given to these processes does not correspond to the fundamental characters of these pathological process.