The LN microenvironment promotes tumor activation and proliferation. (A) The MCL-proliferation score was compared between PBT and LNM groups using unpaired Student t test (left panel). MCL-proliferation scores in matched MCL PBT/LNM (n = 8) samples were compared using paired Student t test (right panel). (B) Representative PBT and LNT samples from 2 patients with MCL were tested for Ki67 using flow cytometry. (C) Comparison of Ki67-positive cells between PBT and LNM (n = 5) samples concomitantly collected from the same patient. (D) The activation markers CD69 and CD80 were measured using flow cytometry in CD5⁺/CD19⁺-gated cells of matched PBT and LNT from 3 patients with MCL. Pearson correlations of the (E) proliferation score in LN biopsies (LNM, n = 34) and (F) the percent Ki67-positive cells in LNM (n = 32) quantified by immunohistochemistry, with the corresponding BCR signature score.