Morphologic and immunohistochemical features of IG/IRF4-positive cases. (A-D) Morphology and immunophenotype of 2 IG/IRF4-positive cases (A-D, case 14; A′-D′, case 20; original magnification ×400): DLBCL component with GC immunophenotype, strong nuclear staining for MUM1, and negativity for BLIMP1. The follicular component of both cases showed an identical immunophenotype (data not shown). Gi indicates Giemsa staining. (E) Differential expression levels of IRF4 (probe set U133A 216986_s_at) between IG/IRF4-positive cases and the other DLBCL subtypes, specifically with the ABC subtype (P = .047). (F) Comparison of the expression levels of BCL6 (2 probes encoding BCL6, 203140_at and 215990_s_at, summarized to BCL6 index) between IG/IRF4-positive cases and the other DLBCL subtypes. Specifically, IG/IRF4-positive cases presented higher expression of BCL6 than the GCB-DLBCLs (P = .012).