Figure 5

Immunohistochemical studies. a) CD79a is diffusely positive. The cells demonstrating strong positivity are reactive B-cells. b) CD20 is only positive in non-neoplastic B-cells in the scattered follicles, and in small amounts in interfollicular reactive cells. c) Bob-1, d) EMA, e) CD138 and f) MUM-1 are diffusely positive. Tumor cells are positive for g) IgA, and negative for h) IgG and i) IgM. j) D2-40 staining revealed no sinus-like structures in the tumor nodule. k) Tumor cell composite depicts absence of κ light chain expression, and l) diffuse cytoplasmic λ light chain expression.