FIGURE 5.

Development of primary CNS lymphoma. Progression of PCNSL (clockwise from top). Initially, neoplastic lymphoid cells accumulate within the vascular wall of arteries and venules fragmenting the reticular fiber network. The outer vascular layer with the glial end-feet maintains an impermeable barrier preventing tumor cells from infiltrating the brain tissue. Later, tumor cells fragment the outer layer and infiltrate brain tissue, where multiple reactive astrocytes can be detected. Endothelial cells undergo regressive as well as reparative changes throughout, leading to disruption of the endothelial lining.