IgG expressing PCMZLs do not express CXCR3. Frozen sections of CM09, CM17, CM04, and MALT21 stained with monoclonal antibodies (in red, 3-amino-9-ethylcarbazole) specific for CD20, CXCR3, and CD3 (original magnification × 400) and counterstained with hematoxylin. IgG-expressing PCMZLs CM09 and CM17 contain CXCR3⁺ T cells, whereas the neoplastic B cells in these tissues are CXCR3⁻. In contrast, CM04, an IgM-expressing PCMZL, is positive for CXCR3, like the salivary gland MZBCL “MALT21.”