Histochemical characteristics of lymphomas. (A-B) Hematoxylin-eosin staining (original magnification, ×400) of P3-L1 (intra-abdominal lymph node biopsy) and P4-L2 (inguinal lymph node biopsy), showing diffuse, massive infiltration by monomorphic large lymphoid cells. (C-F) Immunohistochemical studies on P3-L1 biopsy showing (C) CD20 staining, (D) Ki67 staining, (E) FISH for EBV-encoded RNA, and (F) BCL6 staining. (G-L) CD3, CD8, and granzyme B immunohistochemical studies: in control GCB DLBCL biopsy, (G) CD3 and (H) CD8 T cells were detected at perivascular and intratumor sites. (I) Granzyme B was detected in many T cells. In the IL-10R–deficient DLBCL (P4-L3) biopsy, (J-K) CD3/CD8 T cells were found in the perivascular region, whereas (L) no granzyme B was detected within the tumor (×200 magnification). (M) Counts of granzyme-B-positive cells in 5 control GCB DLBCLs and 7 lymphomas from IL-10R–deficient patients are shown. Counts per optic field (×400 magnification). Horizontal bars represent mean values.