Figure 4D shows sections of a peritoneal tumor mass collected on day 25 from mice xenograft, stained with H&E and examined for the presence of lymphoma cells. Immunohistochemical analysis revealed strong membrane reactivity with antibody to human CD20, cytosolic presence of BCL-6 and Ki-67 as markers of human lymphoma cells (Figure 4D). The liver was involved in all the analyzed animals but BJAB cells were also detected in the bone marrow of 14 mice out of 15 (Figure S3). Here, BCL6 is linked to lymphoma.