B-cell pseudolymphoma – low magnification
LEGEND
Also known as benign lymphocytic hyperplasia
Normal or hyperplastic epidermis
Presence of a Grenz zone and absence of epidermotropism.
The infiltrate is nodular or diffuse, superficial > deep (it extends horizontally rather than vertically, unlike lymphomas).
B-cell pseudolymphoma – High magnification
LEGEND
The infiltrate is much more polymorphous than in lymphomas; it is predominantly composed of lymphocytes, but also includes eosinophils, macrophages, multinucleated giant cells, and plasma cells.
The stroma may become reactive, with edema or fibrosis.
Reactive germinal centers are present with tangible body macrophages and marked proliferation (in contrast to lymphomas, where germinal center proliferation is reduced).
B-cell pseudolymphoma
CD3 expression is positive and more abundant than CD20, which is a reassuring finding.
CD3 expression is shown.
B-cell pseudolymphoma
CD138 expression positive, but weak. CD138 is a plasma cell marker.
B-cell pseudolymphoma
Bcl6 is a nuclear marker of germinal center cells.
Bcl6 expression is positive, with clustering of certain germinal centers visible.
B-cell pseudolymphoma
The kappa/lambda light chain ratio is normal, around 1–2:1 in this case.
Kappa expression is shown.
