Marginal Zone B-cell Lymphoma
A 72 y/o female underwent splenectomy for a massive splenomegaly. The cut surface had multi-nodular appearance. Sections of spleen revealed lymphoid infiltrates (pale cells to the upper left) centered around pre-existing germinal centers (note the dark staining mantle zone lymphocytes to the bottom right of the follicle). The tumor cells were positive for CD20, Bcl-2, and Ki-67. They were negative for CD5 and CD43.