FIG. 2.

Case 1. A and B: Hematoxylin and eosin-stained sections at low and high magnifications, respectively. Granulation tissue with prominent capillary and small vessel proliferation (blue arrows), macrophages and mixed neutrophilic and lymphoplasmacytic inflammation. Vessel with fibrin thrombi shown with red arrow. C: Reactive astrogliosis in the brain parenchyma adjacent to the “pseudocapsule” is highlighted with GFAP immunostaining. D: Abundant reticulin fibers within the granulation tissue (“pseudocapsule”) are depicted with reticulin stain. E: CD163 immunostaining shows marked diffuse infiltration of microglial cells and macrophages in granulation tissue and adjacent brain parenchyma. F: Small CD3⁺ T lymphocytes infiltrated granulation tissue. G: CD4⁺ immune cells. H: A smaller subset of CD8⁺ lymphocytes present. I: Scattered B lymphocytes are highlighted with CD20 immunostaining. J: Aggregates of CD138⁺ plasma cells are noted focally (blue arrows). K and L: Rare cells are highlighted with PD1 and PD-L1 antibodies.