STAT1, TRAF1, and c-REL immunohistochemistry in MLBCL. (A) STAT1 and TRAF1 proteins in MLBCL. A control DLBCL (i, iii) and representative MLBCL (ii, iv) were stained for STAT1 (i, ii) and TRAF1 (iii, iv). Original magnification, × 1000. (B) c-REL immunohistochemistry in MLBCL. A control DLBCL (i,iii,v) and representative MLBCL (ii,iv,vi) are doubly stained for c-REL (iii,iv; green) and propidium iodide (i,ii; nuclear, red). The 2 channels of each case are superimposed in subpanels v and vi. Note predominant nuclear c-REL staining of MLBCL at right (vi) compared with the predominantly cytoplasmic c-REL staining of the control DLBCL on the left (v). Original magnification, × 400.