STAT3 expression in primary lymphoma tumors. (A) Mean STAT3 mRNA levels in tumor samples as assessed by gene-expression profiling. PMBL, primary mediastinal B-cell lymphoma; FL, follicular lymphoma; SLL, small lymphocytic lymphoma; MALT, mucosa-associated lymphoid tissue; FH, follicular hyperplasia; MCL, mantle cell lymphoma; MM, multiple myeloma; BL, Burkitt lymphoma. (B) Histogram of STAT3 mRNA levels in individual ABC DLBCL tumor biopsies. (C) Immunostaining with a p-STAT3 (Tyr705)–specific antibody showing dense brown staining in ABC DLBCL cases. (D) Immunostaining with an antibody recognizing total STAT3 showing dense brown staining in STAT3-high ABC DLBCL cases.