Figure 5. Immunohistochemistry Images.

(A) The arrowheads in the figure indicate some of many areas highlighted in dark brown, representing positivity for cluster of differentiation 20 (CD 20), a B lymphocyte-specific cell surface molecule involved in the development and differentiation of B lymphocytes into plasma cells. The arrowheads also show the areas where the mantle zones are thickened with layers of lymphocytes, resembling an onion skin. (B) The arrowheads in the figure indicate some of many areas highlighted in dark brown, representing positivity for erythroblast transformation specific related gene (ERG) that highlights the proliferating blood vessels. The ERG immunostatin is a member of the ETS gene family of transcription factors, which is highly specific for endothelial cells.