Figure 2

IgG4-negative marginal zone lymphoma (case 16).

There is a diffuse proliferation of small- to medium-sized lymphoid cells (A,B) that are CD20⁺ (C) and CD3⁻ (D). Numerous Igκ⁺ plasma cells are present (E), but only very few Igλ⁺ plasma cells (F). Some IgG⁺ (G) and IgG4⁺ (H) cells are present but the IgG4⁺/IgG⁺ cell ratio is <40%.