PCMZLs develop in a distinct inflammatory environment. (A) Semiquantitative RT-PCR for IFN-γ, CXCL10, IL-12, IL-4, and actin, on whole tissue samples of 10 extranodal MZBCLs (left) and 14 PCMZLs (right); each sample was tested in 2 dilutions. The 2 cases in the middle, CM04 and CM13, represent the IgM⁺ CXCR3⁺ PCMZLs. The lower 2 panels depict the results of immunohistochemistry for CXCR3, and the Ig isotypes determined by RT-PCR. nd indicates not determined. (B) PCR band intensities as determined by densitometry (in arbitrary values). Differences between extranodal MZBCLs on the left and class-switched PCMZLs on the right were significant for IFN-γ (P = .001) and IL-4 (P = .028), as determined by a Mann-Whitney rank-sum test.